the max block subsidy. 1000 coins per block max. It's not 30 days, though, that's the last date that a block will gain more maturity. it's eligible to stake at 8.8 days. Not sure what the general average is a this time, but I'm averaging about 10 days with largish blocks.

At some point, most staking blocks should hit at or near max subsidy. Things will get interesing then