Well, I must be very gentle with my sheets. I can't remember the last time a sheet wore out! Maybe it's because I have been sleeping on my own for the last 27 years!
As for sewing - there's very little involved. I just unpick each end of the corner and pull out the old elastic, then attach a new piece to a safety pin and thread it through, then sew up the ends. However that's 4 corners per sheet and I seem to have accumulated a number of sheets needing this treatment. Feel guilty if replace with new but, sorry PamelaJ , I'm very tempted by Dunelm and Groupon!