I'm using a manual momentary switch to activate ISP so PSEN will only be pulled low for a couple of seconds. I noticed this problem because I initially tried pulling PSEN low through a resistor and found that unless I used very low values (few hundred Ohms) bootloader activation was unreliable. Using a 470R pull-down resistor for PSEN did not give reliable bootloader activation, but a short to 0V does. This seems to indicate the high PSEN current is a requirement for bootloader activation.

The datasheet states "As SPEN has the same structure as P1-P3, the current to force PSEN to 0 as ITL is defined in the DC parameters". The DC paramters list ITL for ports 1-3 as -650uA for Vin = 2V. I find need to draw a lot more than 650uA from PSEN to activate the bootloader.

As ISP is working, this is more of a question of long-term reliability as 30mA seems rather high.