Try Everything 1.5a - an "alpha" version with many improvements, in development for years but inexplicably hidden away on their website. Never experienced any instability.
You should not be starting it when you want to search. You should open it when you log in, and leave it in the tray. It will do a full index on launch then subscribe to filesystem notifications to keep itself up to date for as long as it’s open.
Do that and it’s alarmingly fast and responsive except for the minute or two right after launch.
Contrasting seemingly all the other responses to this, I use it the same way you do (only opening it when needed) and I'm fine with the delay: even at its slowest rebuilding the index and searching is faster than the in-built windows Search.
https://www.voidtools.com/forum/viewtopic.php?t=9787