It's not the most eco-friendly thing I've ever done, but I figure it's a pretty small amount of plastic in the grand scheme of things (especially in my line of work).
One useful exercise is to fret a note as you normally do, and play it. Then keep picking or plucking that note with gradually less pressure applied by your fretting fingers. At some point, the note will choke and not sound out any more. Then, a little more pressure can be applied to make it sound out again. That minimal level of force is going to be the ideal amount for stamina and to prevent injury. There’s nothing to be gained by pressing harder, in fact you can bend notes slightly sharp by pressing really hard. In many forms of instrument practice, hand tension is often the enemy (especially for faster soloing).