I have a pipe going most of the day. When working, I usually have a couple of cobs in the truck, a couple more in my pack or gear bag and one in my mouth. I usually do not smoke the same pipe over and over, sometimes I do if a second pipe is not close at hand.
I have been known to dump, refill and smoke the same cob for a couple of hours and have not found any degradation in the pipe or the taste. I treat my cobs poorly. Briars a bit better. And, my meerschaums are certainly babied, only because they are an entirely different animal from the others.
In the evening I may alternate two meers or smoke four or five bowls using the same pipe. Meers can handle such treatment. I prefer my briars, no matter how many times I've smoked them during the day, to rest until Sunday. Sunday is pipe cleaning day. I've never found consecutive bowls, say four in the morning with the same pipe to have any adverse effect on the pipe.
After each use of any pipe, I dumb the ashes, give it a blow and either reload or put it in my pocket. Pipe cleaners are used only when the pipe starts to smoke annoyingly wet or becomes a bit hard to draw.
If I only smoked a couple of bowls a day I would most likely take only one pipe into the field.