Only if the sum total of all items connected to the thermostat exceed the capacity of the thermostat. Highly unlikely unless you're talking about using a LOT of heat tape. yards and yards and yards
That said, I like to have many different thermostats since I have a large collection. That way if any one fails, I don't have all connected to it. Also, I can set different ones to different temps for defferent species. Lastly, there is always a vertical temp gradient in a stack. The top cage or tub will be warmer than the bottom one. I've started to switch over the Herpstat pro's, with four channels, I can set four different zones in one stack. Or control four different cages all with individual settings and the herpstat pro includes night drop feature..
Outa here, gotta get some sleep, busy day tomorrow so I may not respond again until tomorrow evening.
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Thanks,
Dave Colling

www.rainbows-r-us-reptiles.com
0.1 Wife (WC and still very fiesty)
0.2 kids (CBB, a big part of our selective breeding program)
LOL, to many snakes to list, last count:
21.29 BRB
19.19 BCI
And those are only the breeders 
lots.lots.lots feeder mice and rats 

