My dog runs away - do i buy an electric collar or try less painful alternatives?

Hate to say it but the majority of dogs will not just stay in an area that is not fenced just because you want them to. Some dogs have a stronger desire to wander than others. I have a 12 year old sheltie who has always been a runner when he get the chance, even now at his age. He is high energy and has been trained and has house manners but once in a while the temptation to just have a run is too strong. We walk him regularly and have a good sized rear fenced yard but he was always finding a way to get out (he's brilliant at gates and latches) or he would run through someone's legs out the front door. He enjoys being around us but seems to greatly enjoy the chase, seeing it as a game. He comes back a few minutes later panting and happy and wanting to hang with us for a while. I went to an invisible fence about 3 years ago and it works a lot better but I had to use three separate lines of fence about 10 feet apart and a stubborn dog collar. He is smart- he has learned the boundaries and as far as I can see never gets shocked. They have radio fences (invisible fencing) that can cover several acres and you may have to fence off a few acres around the farm for him. It saves us a lot of aggravation. We do not let him off lead if there is a chance he can run off. I have another dog that generally stays close and can be let off lead considerably more places than the sheltie.