RUNNERS: Is it a good idea to get 2 pairs of the same running shoe you love on sale so you can switch between them?

I bought on sale the same model in different colors of my favorite pairs of running shoes cuz I run about 30miles a week, give or take, and so instead of paying aroun $70-$90 every 6-9months on running shoes, I found 2 new pairs on ebay for $50 and the other $60 and wanted to know if there is any benefits to switching between two pairs of the same shoe?
Thanks! :)
RUNNERS: Is it a good idea to get 2 pairs of the same running shoe you love on sale so you can switch between them?
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