My argument against 5s revolves around the idea of throwing angle. Currently 4 sec must be thrown at a low angle to allow it to settle, making it impossible or nearly impossible to roller a good hide. 5 sec would allow nades to be thrown at the same angle that you would throw a 3 sec, making it easier to hit the same hide. 5 sec nades would make contact nades to open hides mostly redundant, and I regard opening hides an important part of the bng meta game.
On first review, this might seem like it favors the lamers, but I think the top players would benefit more from 5 secs, and I don't think the scheme needs more division between the top players and the newer players, bng has a very steep learning curve, one of the hardest outside of ttrr. Then again, 5 sec could make the scheme more fair in that a map with one side with better hides than the other would be more or less negated because more hides would be reachable with 5sec nades.
It would be advisable to test before changing the rules here, I feel allowing 5secs would be more drastic than some of the other changes suggested here.