I have an early (?) 2015 MacBook Air Model 7,2 with an i5, 8gb, and a 251gb SSD with about 200gb available. Was reading somewhere that perhaps upgrading the OS to Big Sur may be of marginal value on older machines. Was wondering if upgrading mine would be recommended. I have also read that I have essential "paid" for OS upgrades through the purchase of the Mac, so should do it. However, I do recognize there is going to come a time when there may be diminishing returns. Would like some input. Thanks!