Thermostat

[Jeff &/or Paula <jknipe9@idt.net>]

Could someone tell me the temperature range for the engine air-cooling
thermostat?   And, at the risk of opening a can of worms, your opinions
on the thermostat/flap assembly?  As I think everyone has read, some
don't reinstall it to avoid the possibility of failure and subsequent
overheating, others maintain it in the interest of quick warm-ups. 
Would like to know what you who really work with these engines think. 
Thanks.