become gold before longhaulflight
 

I will be able to gain gold status before my year end in November. So i do not need to do a TP run for that.
In October i will do a longhaul flight from the US back to Europe. When getting on board of that flight i will have 1485 TP. Does it make sense to do a 20 point run before that flight so actually taking the longhaulflight as gold instead of gaining that status just after the flight?

Will it have benefits to board as gold instead of silver?

If yes, what would be the cheapest way of gaining 20 points on a b2b flying from amsterdam, dusseldorf or brussels?

I guess the key benefits will be, maybe a better AA lounge or BA lounge from the US depending on your departure airport, Galleries First in LHR (assuming you're connecting), you'll get a better benefit from the higher Avios bonus, plus you'll get to board with Group 1.. onboard nothing will be different ( there's a theoretical chance you'll get a greeting on board, but that's not guaranteed.)

Cheapest 20TP would probably be AMS-LGW-AMS (just guessing) and this should get you 20 TPs (10 each way) as long as you avoid the booking classes O,Q and G

Since you are departing the USA it would depend on the airport as to whether (e.g.) there was First lounge provision (mostly that isn't a big deal). Plus there may be additional baggage allowances, if relevant. Using the First Wing as a short cut alternative to Flight Connections (assuming Europe doesn't mean UK......) would also be worthwhile to some extent but the time to do a TP run (and consequential security) wouldn't make for a strong case You could do a calculation on the extra Avios side to see if it's worth a TP run, which I suspect is unlikely, the cheapest is likely to be something like LGW-EDI or GLA, but see the TP run thread or the myriad other threads asking similar question to get inspiration.