How often should you swap stirrup leathers

Not sure, but last time I had my saddle re-flocked and checked, lady said to keep an eye on them for this and also to watch the straps they attach to on the saddle (can't think of the proper technical name for 'em!). I have stretched a pair of mine so that one is longer (just slightly) than the other. Most annoying as it makes me wriggle about somewhat and I am always wondering if the saddle has slipped!
 
Thank you for this post. For 6 years I used a lovely pair of leathers which I took along and fitted to the RS saddle every time I hacked. I fitted them at random so never worried about equalising the sides.
But 3 months ago I left my new leathers on the share horse saddle and it hasnt crossed my mind that I should switch them over! Thank you for reminding me. The real question might be how many rides?
It is odd to think I have spent a whole twenty four hours sitting on her. No wonder we get to know our horses.
 
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