in my experience transistors can work quite hapily but be to hot to touch
for any lenght of time,
however i seem to have more sensitive fingers than most people,
also if it leaves a mark on your finger or even takes skin off then i would
say its too hot, especialy if it has any heatsink.
this ocurs much above 60'c i think wich means the silicon is probably a lot
but typicaly silicon devices are speced up to over 100'c, but reliability
goes down with increasing temp.
It is not uncommon for say automotive spec devices to operate between -40 to
125degC (- 105 + 20degC Delta for board temp) and junction temperatures of
upto 150degC. Check the datasheet for that device, it should have the
operating temperature range. If the pervoius device did not get hot then
the char. of that transistor must differer to the original and how much more
"heat" it can withstand will again be in the datasheet.