How durable are those clips? After being used for awhile, to adjust the height, should they be replaced? I can't see any easy way to retighten them as they don't appear to be standard C-clips with holes to remove/install.

 

You should find a height that suits you, then leave it alone. Alignment settings change (toe and camber) when the ride height changes, so it would be in your best interest to get the car aligned after you have found a setting you like. I haven't changed mine in over a year, with no signs of any problems.