Will keeping a clip loaded wear out the spring?

The spring is theoretically designed to take it . However, I would keep it one round short of a full magazine. That cuts the spring stress to less than half. You can test that yourself by measuring the force required to put the next to the last round in compared with the last round. It is a big difference. Why stress the spring unnecessarily?

I keep mine loaded not only with a full clip but also with one in the pipe and have never had a problem.

I suppose that eventually it might. I know that the Soviets made a key-wound drum magazine for their AKs to prevent spring fatigue, but that stuff can be weird anyway.

If you google Glock magazine springs you will see many for sale. Here is an example. They are selling these springs because people need to replace them. And why do they need to replace them? Because the spring no longer functions correctly. And what makes a spring not function correctly? Overstress or corrosion. And how do you overstress a magazine spring?
You greatly increase the stress by jamming in that last round.
By putting in one fewer than the max you cut the stress tremendously. That greatly increases your spring life.

Yes the spring will wear out but it will take a long time. Longer than you will most likely have the mag for anyway.

Mag springs wear from repeated compression and relaxation. Keeping them loaded constantly won’t wear them out. People who participate in IDPA matches will replace mag springs from time to time because they may “actually” wear them down.
@Nullo The Soviets had the top loaded drums that were under constant spring tension. They are good mags still. The Chinese figured out how to make them so they could be opened up from the back and leave leave the spring relaxed but still keep them full. Those are different style of springs, like in a watch as apposed to a coil type that are in slab mags. I should try that in mine some day but at over 100 bucks a copy I’m not anxious to really find out. I still keep it maxed out with the 75 but leave it un- wound. I fired out a full drum one time only to see if it functioned right and haven’t used it since. A 75 rd drum attached to an AK is too heavy to really be practical but they are fun.