Agree with lescef. We had Humphrey on a long line for a couple of months and I used to try and do a recall everytime he‘d just about reached the end of the line and he soon got the message re the distance he could go, he‘s rarely further than about 10 meters away from me now. Another good idea is to praise him everytime he stops and turns to look at you, he doesn‘t necessarily need to come back everytime, (unless you‘ve given a recall command of course, but it gets him into the habit of remembering to check where you are instead of just forgetting you‘re even there and going off to do his own thing.
I practise recalls on EVERY walk, sometimes with a whistle, sometimes voice only, it needs drumming in a life long in my opinion. Sometimes he‘ll get a treat, sometimes more (I‘ll make him sit and then give him perhaps 5, at intervals, so he learns its worth staying put!), sometimes a game. Try to avoid only recalling when he has to go back on the lead, coming back to you has got to worth his while (in his opinion!), and needs to be more exciting than what he‘s doing at the time! My first trainer told us most dogs mature at around 2 years but winked and added that for cockers, read 3 !!! I thought she was joking - she wasn‘t !!!