I guess the reason for all those 0 - 1 second intervals between longpolls are somehow due to p2pool popularity increase / many people giving it a try, let's hope it will stabilize somehow, so web have at least a few seconds between longpolls 
Nope. This is only function of share diff, pool rate and luck - more share diff shares posted in row to chain. Maybe you see moment when some 10GH or more user join and put few shares on lower diff b4 pool catch this and increase share diff to keep avg 10s longpool Scan time 60 is good enough, I never see longer longpool interval.