I used my Thermocell at the end of last year before it got cold. There was a yard that I hunted multiple times, but the mosquitoes and gnats ate me up toward the back. I turned the Thermocell on and only used it for about 30 minutes and then turned it off. Seemed to be enough to drive them away from the area where I was searching. BTW, I used to carry it on my side pouch when I detected, with the top sticking out, but I just recently bought a holster.
I also used it for a couple of soccer games and outings that I went to. I placed it on the bench where everyone sat and it cleared the mosquitoes out. I think that the unit cost like $22 with a butane cartridge and 3 pads. The holster was around $12. I bought a refill kit which will last me 3 months, because I don't use it all the time. It smells a little like something is hot, but to me it doesn't stink or anything. There is also a no-scent cartridge which is used for hunting, but I haven't used it.
If you PM me your email address, the company will give you a discount on buying a unit.