Longevity, as at least a solid top four defenseman:
35 is probably safe for most top defensemen, 36-38 is more iffy, over 38 cross your fingers.
Ray Bourque was playing 26 minutes a night in his last season at 40.
Scott Stevens last full season was at 38, 23 minutes TOI
Lidstrom 41
Chelios started to break down at 39, but still played 24 TOI at 41 over 66 games
Chara's last 24 minute year was at 38, at 40 only 22 minutes a night
Weinrich went from first to second pair minutes at 35, played until 39
Housley last full year at 37
Markov last full year at 37, dinged at 38
Leetch last year was 37, dinged a bit.
Campbell last full year at 36, 18:26 at 37.
Neidermayer last year at 36, played 26 minutes a night
Schneider started getting dinged at 36, still 67g, 21 TOI at 39
Zubov last full year at 36.
Wesley last top 4 year was at 35, 3rd pair through 39
Numminen started slipping at 35, last full season at 38
Coffey wasn't the same after 34, though he played to 38
Hatcher last full year at 34.
Desjardins last full year at 33.
Svoboda last full year at 33