close your windows.(just kidding)
30 yrs. is a good life for a furnace, i wouldn't want to be paying your bills.
alot can happen to a 30 yr.old furnace in 2 months,kind of like a 90 year old person, you just never know.
i'd recommend calling a tech back out. hopefully it's something inexpensive to fix, but you should consider getting an estimate for a newer higher efficient model.
good luck