Is there a standard that tells you how many times you can replace a PBGA without reliability issues? I've read IPC-7095 (many times) and have not found a recommendation for this. We have Class 3 products.My thoughts are 2 times max.
We place PBGAs with a reflow system - not reflow oven.
Two BGA replacements (same location) and throw the card away is the rule we are following. Experience has taught us that anything beyond this and you'd be pushing it - specifically when your new PBGA's price is above $20.00.
The biggest concern is when dressing the site after removal of device and how careful the operator is ... the pads can't take much of the heat exposure and friction forces (if using solder wick for cleaning).