Puffs:
The purpose of resting a pipe is so it can drive when you're too tired.
Actually, like just about everything else in the pipeweedic world, there are no hard and fast rules. It depends on the pipe. In my
experience, I only need to dry out a pipe that's wet. Not every pipe gets wet on every smoke. I have some old Caminettos that consistently give the most wonderfully dry smokes. When I get to the bottom, there's nothing but dry ash, and I can reload the pipe and go again if I want. So much depends on the moisture in the tobacco, P-V-T (pressure, volume, temperature) of the ambient air, its relative humidity, the thermodynamics of the pipe itself, the way you smoke, how often you swab out accumulated condensate with a pipe cleaner while you're smoking, and of course the construction of the pipe (e.g., if it's a bent pipe, does it have a moisture trap, or does condensate run back into the bowl?).
For that matter, do you really need to "dry out" a pipe in the first place? Well, if a wet heel doesn't affect the way the pipe smokes or the taste of the tobacco, and you want to burn another bowl, it's your call. I've done it, and I've never seen any long-term ill effects from it. I don't do it as a habit, because I seldom want to smoke two bowls of the same tobacco back-to-back. When it does happen, I don't have any hesitation about reloading and relighting. But I'm usually ready to smoke something else by the time I've finished a bowl, so my pipes usually get time to dry out anyway. It's not something to which I've ever needed to give much attention. Of course, having more pipes than a person could possibly need might have something to do with it. But then, "need" is a relative term.
I wouldn't set a pipe in the sunlight unless I wanted to sun-bleach it to a lighter color, or bake out some residue of a previously burned tobacco, or some other objectionable taste or odor. I use sunlight when I want to do an inspection that requires a light source more intense than any artificial source I have, but I don't leave the pipe there. The only time I've ever done that is when I bought an estate pipe that must have been stored unsmoked in a very damp place for a long time, and had a foul odor. The sunlight treatment helped, but I probably would have needed to repeat it many times for greater effect. Ditto the rock salt and alcohol treatment. I think the thing that has made the most difference is just smoking it...with straight Latakia. :heart: Yum! Due to the graces of pure Latweed, the odor problem has slowly gotten better. If I ever get a round tuit, I'm going to send the pipe to LL and let him whup his magic on it.
In any case, I wouldn't put any pipe near a heating vent. I could probably come up with reasons if I thought about it, but my intuition tells me that it's a pretty severe thing to do. My preliminary sense is that it could cause expansion/contraction fatigue on the mortise and tenon. Also, a forced air heating vent usually contains very low humidity. I'm not so sure it's a good idea to expose a pipe to such severe high-temperature, low-humidity conditions. Just doesn't seem like a good thing to do.
If the pipe is wet, why not just get another pipe off the rack? If it's a tobacco you really like to smoke, you'll probably have more than one pipe dedicated to it anyway.
Vito