Guts initially go through a lot of stretching when new and then settle down but they're always going to be affected by temperature change. If your house is colder at night, often they'll be sharp in the morning, etc. Bring your bass into a club from the car and it goes wacko. Then they'll stretch from playing, contract from the climate, etc., it just goes with the territory. Gut is an organic material, like skin or leather.
When I have a gig, I try to set my bass on the stage for 10 minutes or so to get acclimated, tune, then play for a few minutes and tune again. At that point, if the temperature is reasonably stable, the bass will stay in tune fairly well. I still keep one of those Boss tuners that mute the sound when you step on it in line when playing amplified and do quick tuning checks.
Yes, it's a pain, but you've got to suffer for that gut sound! Or else get some synthetic strings
