It depends on your preferences, but for me the $1700 would definitely be worth it because of some of the benefits of Plt, specifically:

1) room upgrades, since I typically spend a lot of time in the room when on the road for work
2) access to the SPG Plt phone line, which has always been great when dealing with issues or helping me out with my sometimes-ridiculous needs and requests
3) the ability to always get a room (even though sometimes must pay RACK rates) even at sold-out/oversold, etc. properties, since I often book popular destinations day-before or day-of

That said, with all the bonuses you're getting, the value of the 41,764 points alone is worth almost $1700. At that rate, you're earning a point for every $0.04 spent. SPG points are typically worth between $0.03 and $0.04 each, so the value of what you're earning is almost as much as what you're paying to earn it. My last few redemptions with SPG have been:

1) 12,000 pts for a $600/nt room at the W New York where I was upgraded to a $1,200/nt suite because of Plt, and then given almost $200 in food and drink coupons since my room (the upgraded suite, not the original) was not ready when I arrived to check in at 6pm
2) 10,000 pts for a $360/nt room at the Sheraton Commander Boston
3) 10,000 pts for a $450/nt room at the Sheraton Suites Calgary
4) 12,000 pts for a $340/nt room at the W Tuscay in NYC

As for paying and then not checking out...

I haven't actually checked out of a hotel in 3 years - I always just leave at the end of the res - and haven't run into any problems. Even though its probably bad practice to not check out, I can tell you that in 136 hotel stays over the last 3 years I haven't hit any snags with not checking out.

Others may have experience with leaving days before the end of the res (I have never done this), but I have heard of housekeeping checking people out when they see that the guest's belongings are all gone. A couple of thoughts on that...

1) I would tell the hotel upon check-in that you will be "in and out" of the room and that they should not assume you've checked out because your stuff is gone. Let them know that you intend to pay for the full 15 day block even if you are not physically in the room the whole time (they don't have to know that once you leave the first time you are gone for good)
2) Leave the "Do not disturb" on the door when you depart. That will hopefully prevent housekeeping from coming in and checking you out of the room.

Good luck!