We don't wean, unless there's a reason to, up until getting close to tupping. Most of our lambs will be away in their first season anyway, so a lot of the ewes get weaned as their lambs are sent away. Like you, we have quite a few boys left entire, so they get collected up and taken off before they are likely to find any mischief (which we didn't do early enough last year - note to self, remember to do this before the end of August this year

.)
Assuming you won't breed your keeping ewe lambs this year, there'll be a point at which you separate them from the ewes before the tup goes in in any case, so that would be when they get weaned.
If the grass is poor, and/or the ewes seem in poor condition, you might decide to bring that forward. Otherwise if the ewes seem healthy and well-fleshed, and are on good grass, then there probably isn't much harm done leaving their daughters with them up until maybe a month before tupping.
If you like to flush your ewes hard, then this might not be long enough; the ewes may need a couple of months to recover. We're at the other end of the spectrum, we'd prefer every ewe to have a good strong single, so we try to not flush.