How Long Should It Really Take?

We use our clothes dryer much less than most families, I assume. For one thing, we never put our shirts or pants in the dryer, but instead hang them up to dry in one of the bathrooms. We've been doing that for pretty much the entire time Vicki and I have been together, which is now 20+ years (almost 19 years of which we've been married). For the laundry load that includes towels, socks and underwear, during the non-winter months (April through November, say) we hang those items up outside, on the spinner rack that's inconspicuously located in a corner of our backyard. That means that, for most of the year, we don't use the dryer at all. In the cold months, we use it for about every third load that comes out of the washing machine.

Because of that, I go months without using the dryer, every year. Therefore I'm not as "attuned" to its workings as I am the washing machine, which gets used 3 or 4 times per week, all year round. This winter it seems like the dryer is taking longer than usual to dry its load. I don't think the quantity of each batch is any bigger, and yet it seems to take at least 3 hours where previously I would've said it was 1.5 to 2 hours. Is this an indication that the machine is performing sub-optimally now, or am I just mis-remembering the duration because I use the machine so rarely? Any laundry experts out there who can offer up some insight?

[Update # 1: Based on the comments left so far, Vicki and I detached the thick metal hose from the back, looking for a big clump of lint in it. While we couldn't access the entire length of it, for the parts that we could get at, there were lots of bits of lint, but no big, obvious wedge. We cleaned out what we could find, and put it back together. I'm about to try a load of bedsheets in it, to see if the results are any different now. One thing struck me as curious, though: the air coming out of the hose, when we turned the dryer on - empty - for a few minutes, starting off warm but then quickly went to cool. I would've expected it to be hot or warm the entire time. So perhaps the problem is that the dryer's heat source isn't working very well, and that's why drying is taking so long? (Oh, and as Tammy notes: I'm the type who cleans the topside, easy-to-access lint trap out between every load, so that's not a worry.]