Thanks for the replies.

When I fired up the boiler for the first time last month, I cranked it
to 80 for about an hour and checked each apt to see if the radiators
were getting hot, which they were. And I also replaced any suspect air
valves. So the radiators themselves are fine. Its just the setting on
the T-stat. This is my first winter with this bldg. The old landlord
had a Honeywell single dial T-stat set at one temp 24 hrs. Not real
energy efficient, so I replaced it with a programmable one.

I also told each tenant don't bother calling me to complain about the
heat if your A/C's are still in the windows. God I hate when people do
that.