Let me start off by saying this Heater works GREAT ! Now, as far as the Accuracy of the Temperature Control / Thermostat, well that has a little bit of a Learning Curve. It runs a little under what the Gauge says, by like maybe 3 Degrees – That being said once you “Calibrate” it with a good Thermometer (I used two Floaters for comparison, until I saw they both read the exact same temp for a week – I took one out. This Heater’s “Gauge” was set at 80-ish, maybe 82 – The Water Temp settled in at 77. Not Bad. Just an Informational Tool. I have had this now going on 4 Months and it is Running Great – Once you Figure Out the Gauge, as I am thinking maybe they are all a bit different, you will know where to set it – I will say this, If I turn it down two degrees, it lowers the water temp two degrees and vice-versa. It stays put, though the suction cups should be on longer stems as the Top of the Heater presses the Tanks Edge and the Top Suction Cup Barely meets the glass – a 1/4″ Longer Stem From the Heater Clamp to the Cups would be Perfect. But, like I said it stays put so Mission Barely Accomplished There. The Temp Control Knob is Tight to Turn – Which I guess feels better than if it were loose, But, you do have to grip it to adjust the Temp. I love the Glowing Amber Light that shows it’s on and the Warm Red Glow you can See thru the Glass, lets you know it is heating evenly from top to bottom of the Wired Grid. I have had more expensive Heaters that didn’t warm evenly – AND, I was skeptical due to the low price but the Quality of the Build is Really Good. It’s a Solid Little Performer so far. As for Longevity ? We’ll see !( I bought a Second one for my New 75 Gallon Tank) – When I first Plugged it in on the 20 Gallon, the Water was a Chilled Room Temp of 70 Degrees (F) – It took a Minute (Slang) to get it to 80 but has held steady ever since – Maybe 6-8 Hours to get there – IDK – I didn’t really time it. After I learned it’s Gauging “Idiosyncrasies”, I found where it hits 77, though the Gauge says 80-81? It shows more like a sliding scale anyway so be your own judge on that. As for me, I Like It.