If you're using a WE GBBR...
1. Avoid the first generation 30 round STANAG magazines, they are horrible for leaking
2. The second generation 30 round STANAG magazines are much better, they took the design of the 20 round magazines which also is much better
3. Accept your magazines are wear items and there is high potential you'll have to replace them, on the plus side WE makes a refurbishment kit for first generation magazines