Right now I have Earendil in a 1 gallon tank with a Bettatherm Betta Bowl Heater. It's been pretty good at keeping the temperature about 10 degrees higher than room temperature, but the temp in my room can vary quite a lot (especially if we're going in and out of the room often). Myself or my husband are home generally at least every few hours, so I've just been keeping a really close eye on it. There have been a couple times when it's gone up to 85 / 86 Fahrenheit, and I've unplugged it for a couple of hours and then plugged it back in when it goes back down to 78 or so. It usually runs between 78 and 83.
I also have the empty tank with the Top Fin 25 Watt adjustable heater. I have it running for the plants, and the heater seems to be working just fine. I've also ordered a nice Eheim Jager 25 Watt adjustable heater, but it won't get here until sometime next week.
I'm leaving Wednesday night for Thanksgiving and won't be back till Friday night at the earliest (maybe sometime Sunday). My roommates will be gone on Thursday, but will be back after that and will feed Earendil twice a day on Friday / Saturday / Sunday if needed. I'll do a 60% water change right before I leave, and I think it should be fine till I'm back. What I'm worried about is the heater. Should I move Earendil to the other tank with the Top Fin heater, or will he be better off staying in the tank he's in and maybe having the temperature go up to 86 / 87 for a couple hours once in a while?