In my honest opinion, that is more than fine.
Bear in mind, that if he is a key player for the team, he might not wanna let him go, no matter what you offer.
I personally have had a few of those players, not that old though
Negotiation is kind of a joker, you never know if you are ignored or close or just plainly rejected.
Most manager that doesn't want to sell keeps the offer open all the 24 hours to make the point of a stupid offer or the reluctance to sell.
