It's May 2021 now so it's been running for 2.5 years. I use a glass thermometer to make sure the temperature stays within an acceptable range and my hands are in the water at least once or twice a week to clean the glass, trim plants, or do other aquarium maintenance, so when the water gets too hot is or too cold, I would have caught him. I can't speak for the water temperature being constant, but water temperature is not inherently constant and slight fluctuations don't seem to bother my fish and neither do I.
Convector Electrolux ECH/T-2000 M, white
21 Review
Faucet water heater with display
13 Review
๐ Fluval E300 Electronic Heater - 300W Advanced Aquarium Heater for Tanks up to 100 Gallons (A774)
9 Review
Hardy Leaf Black Forest Asian Java Fern Potted Live Water Aquatic Aquarium Plants For Freshwater Fish Tank By Greenpro Microsorum Pteropus
39 Review
๐งฒ Efficient Magnetic Fish Tank Cleaner: KEDSUM Floating Clean Brush with Handle Design
34 Review
Efficient 2-In-1 Magnetic Fish Tank Cleaner With Non-Slip Design And Scratch-Free Blades
37 Review
Steam cleaner Deerma Deerma DEM-ZQ610 EU, white/red
68 Review
Vacuum cleaner TEQQO Aquastick 3 in 1 Power, grey/turquoise
26 Review