Hi Boxerr, firstly don't buy a whole new pump if one fails. The pump can be bought for as little as $40 Au in an autoparts shop. The same pump fits many cars. A friend of mine had one fail in a G650gS and also in an R1150RT. I suggested that he took the pump to an autoparts shop in Canberra and see if they had one the same. Sure enough an exact same pump $40. BMW want to sell the whole pump, filter and everything but that is not necessary.
Yes the rubbers that hold the pump can fail after a while. They too can be replaced.
There have been problems with the top of the tank where the pump mounts cracking but there is a part from a BMW car that is exactly the same but much cheaper.
Have a look here
https://www.crossroadz.com.au/F650GS/FuelSysRepair.html
good luck and have fun
pete

 

Also the flexible plastic straw can fail, might be useful to have a look on the Crossroads link and see what else will fit .
If going overseas I would suggest packing a spare pump and corrugated straw. Small and easy to fit in
Oh and remember fuel pumps hate running dry, do your best not to run out of fuel

Pete