Which plugin are you referring to that you don't bother with? The main one I know of is honey, which is automated, and takes about ten seconds while they run through the most popular, and if you choose to continue they'll run through the full list of recently valid coupons which adds at most another twenty seconds. 30 seconds of time to save 10 to 30 percent most of the time is worth it to me. The only time I ever think to skip the check is on sites like Amazon or Wal-Mart where the majority of coupons are for very specific items. But even on sites like Jet and Target I often get lucky.