I have a working Cocker, so same kinda energy as a Springer. He was exactly the same as yours at 10 months old. He was fricking WILD. Mouthing, jumping up to grab sleeves, darting into the cupboard to steal shoes, started chasing birds, started sloping off under bushes to avoid being re-leashed at the ends of walks, all kinds of crap. Loads of destructive chewing, constantly frittering about, etc.
He’s nearly 18 months now and the edges have definitely softened. I’d say you can usually start to see maturity around 1.5-2 years old (maturity relative to a Spaniel, I mean!…)
When you enforce naps, is it on a schedule? Or just whenever he’s being too wild?
What did it for us was to have a structure for him. Enforced naps in the late morning, mid afternoon, and then late evening. That coupled with Relaxation Protocol (“settle”) and impulse control training, etc., solved the problem. Over time, he started to settle himself at those times of day without the need to enforce it.
Kong Lock-It balls were also a lifesaver and could keep him busy for up to half an hour if I froze them or put a cocktail sausage inside sideways, haha.
Also, I stopped giving him constant stuff to do, as I felt it just kept him alert expecting more and more stuff.
Instead, I created a routine of like… enrichment in the morning (kong balls, cardboard box, whatever). Then a walk at some point. Afternoon training and play. Evening - natural chew and no games. This really helped. Basically, one activity per time of day.