Screw on the stair gate without drilling into the stair railing

Up to what age do you actually leave the gates in? Our little one (2 3/4) climbs up quite well, so I'm thinking of removing the one below soon, but I would still leave the one above in for a while.

Our [ist jetzt 2,5] and for 2 months now we have had no grids either at the top or bottom...

Our eldest is 2 1/2 and the gates are usually open. Now the little one, at 7 months, is already very actively starting to pull himself up on things and climb stairs, so they are being closed again now

All almost the same age.

Our gate is usually open during the day as well, but when the little one soon stumbles to the toilet at night, we at least planned to close it again in the evening. Our bathroom light switch is somewhat inconveniently located for children just before the first step of the stairs.

You have the outside seating? I know that from before - but today?

Just a very quick off-topic question.

Yep, that one is outside. Inside we have the open shower, so it was not allowed to place it in the bathroom.