I think it also depends on the age of your dogs and what stage of maturity they're at. Mine are 3 & 5yrs now and we're not as focused as you as primarily my dogs are family companions and we like hiking and cycling together. So I train them enough so that they are mentally stimulated and at a reasonable level of obedience. We've tried heelwork to music and agility but it's not really 'us'. Dave enjoys it the most, but Normy thinks it's ridiculous, she'll master stuff like that really quickly then throw herself on the floor in a strop if I ask her to do it again
So because they both enjoy basic gundog and obedience we do that mostly and I sometimes do some tricks with Dave.
I do find that both of them will tell me when they've had enough and they both like breaks from training at times too. I'd just say be guided by your dogs, if they're going stale on things or becoming a bit too frantic, knock it on the head for a while until you find a balance you're all happy with
I prefer to train at good moments when opportunities arrive, rather than planning to do it if that makes sense so most exercises we do are relevent to where we are and what we're doing. If we're in a field with some shrubs/trees they get sent off to track and flush, in the woods I'll hide a dummy for them, on lanes we'll practice heelwork or some other basic obedience and at home it's hide and seek or a few tricks for Dave but I we just do it for a few mins when I've got spare time and they're in the right mood and not every day.
I find even basic things need a break at times - both mine have very good recall for example, but my Weim is having a bit of a funny time at the moment so I've walked where I can leave her to her own devices for a couple of weeks and she's much keener now and less 'I'll do it when I'm ready'.... bless her
I'd say it is important to let them relax as they'll always be times when you can't offer as much so it's harder for them to handle those times if they're used to being 'too' occupied if that makes sense?
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