Unless she's Mother Theresa. Shagging Mother Theresa is commendable even posthumously.
Be honest (because 'commendable' is an interesting word) are you doing this - against your better judgement - because there's a scenario in your head where after half a dozen 'shags' he declares his undying love and you give him the brush off? Because, if it is that, it ain't gonna happen. Instead, you'll be clinging to his knees while he drops a post-coital Kleenex in YOUR bin and announces he 'can't do this anymore' because he's moving in with a 25 year old Russian speaking kindergarten teacher, called Celeste, whose father owns Costa Coffee.
Trust me. This will NOT end well.