SmartTrip Metro Cards
 

Are these the best option for travelling around on the Metro?

Going to be flying into Dulles and then taking the bus to West Church Falls (or some combination of those words) station. Then catching the metro to McPherson.
The following day, going to L'Enfant Plaza with trips to the DC Armory, Pentagon area and back before finally going to DCA for a flight. (7 journeys min.)
Might be some other trips if I'm too lazy to walk. Not sure how spread out things are compared to say New York. Use the subway with an umlimted travel pass whilst there and get my money's worth!

Can I buy the SmartTrip cards or passes at any station?

It's not worth getting a SmartTrip card for such a short stay. It costs $5 http://www.wmata.com/fares/smartrip/ and you really won't save that much money in 24 hours. You can buy a one-day pass http://www.wmata.com/fares/purchase/passes.cfm

If trying to save money, look into bs 5A to Roslyn metro, then metro to McPherson from there. Agree day pass is best bet, but you would have to pay for bus with cash, i dont thimk the driver can sell you a pass and there is no machine at Dulles

Correct - the 5A driver sells nothing; and you can't buy any passes at the airport. Note that while the One Day Pass for $9 could be useful it has restrictions: it is a rail-only pass, and it can't be used before 9:30am on weekdays.

If the OP has enough time before the trip to the DC area, you can buy a SmarTrip card in advance. It costs $30 - $5 for the card, and it includes $25 worth of fare. There are no mailing or handling fees added. The SmarTrip card can then be used for the 5A bus trip into town, and all the other Metro rail and bus travel. See: http://www.wmata.com/fares/purchase/store/

But a one day pass may still provide better vale. I suggest thebOP total their fares for the metro trips and compare it to the flat fare of a one day pass. Note the time of daynfor travel can effect the fare price

Going to be there from this Thursday afternoon until Monday morning so no chance of getting a pass mailed to me.
Will probably require more than a day pass and since I've got the small matter of a marathon at the weekend, will be heading out towards the Pentagon at around 5:30am on Sunday. It's recommended to have a pass already in place due to the amount of people travelling back and forth around that time.
My flight from DCA is around 11:15am so wll probably leave my hotel before 9:30am to catch that.

You can buy farecards at any station. For a weekend trip, I wouldn't recommend getting a SmarTrip card; they're useful for residents and repeat visitors, though, mostly for making bus transfers easier.

Rail day passes can be purchased in advance from any farecard machine; they're validated upon first use (and good until 4AM the following day, but again not valid before 9:30AM on weekdays).

I'd say that depends on whether the OP is visiting D.C. more than once. I moved from D.C. to NY over 10 years ago and kept my SmarTrip card for use whenever I visit. Saves me a few minutes each time since I don't have to buy a new farecard each visit. That's easily been worth the $5 investment.

the falls church bus is privately operated and won't accept SmarTrip.

You can take the public bus to Rosslyn onto L'Enfant Plaza

the public bus is also cheaper

10 years is a long life for a smartcard. I personally am very careful with mine and have had it for around 10 years, but several friends have had theirs snap or simply stop working on more than one occasion.

Well, used a mixture of things.

Used the Washington Flyer for $10 to West Falls Church.
Paid $3.85 to McPherson as it was peak time.
Following day bought a 1 day travel card for $9 and used that a bit.
After that, just paid as I travelled as trips were only $1.85 as it was the weekend - easy enough to put $3.70 on a card for a return.

Some Metro stops are not in the best location anyway. Found that L'Enfant to the Capitol Building is around 3-4 blocks and that takes you onto the Mall.
If you get the Metro, you've a walk slightly uphill for a few 100m to the east side / Library of Congress and the better photo opportunities are from the west in my opinion.

99% of the time it just sits in a pouch in my briefcase, so the wear and tear is minimal. If I have a trip to DC, I put it in my wallet for that period of time. It's held up fine.

Emphasis on Stored
 

Hello,

I'm in the DC area just about once a year for two days only, but have had a smartrip card for a few years now. I forget every year whether or not the card was able to be used, thus has anyone had an auspicious time on the metro with the card after nearly a year has elapsed?

Thanks,
TBS

You'll be fine. The cards have a service life of several years (see above), and the balance does not expire. Do register your card at wmata.com, so that the balance is protected even if you lose the card.

Metrorail's paper fare cards, though, only carry value for a year or so; the mag stripe fades. After that, you won't be able to use them at the turnstiles but you should be able to trade them in for fresh cards (or transfer their value to a SmarTrip card) at a vending machine or at the Metro Center customer service counters.

There is also talk that WMATA will make fares more expensive for paper farecards, effectively giving SmarTrip card a discount.