Possible over heating

My car just became road worthy today. Aside from the brake problem I posted a thread about there may be potential for an over heating problem. When it warms up the temp guage stays around the half way point while in motion (which seems a bit high to me). At a stop sign/ light it creeps up closer to the 3/4 mark then goes back down to half when traveling. To my knowledge the fan kicks in when its suposed to. Am I being paranoid? or is this around normal Op. temp for a Corsica. I also have yet to replace the coolant that has been in there for almost 2 years. Could that be the problem? Thanks

normal actually, the fan turns on at the last minute in these cars. We drove our around for about 6 months with no fan running in it.

The problem seems to have worked itself out although after long freeway trips it gets a bit warm. The fan is working properly so I think I have narrowed down to either the extremely old coolant or the thermostat (which is relatively unused but again sat for 2 years with old coolant).
Again thanks for the reply.