As a punter, I have accounts with 8 or 9 bookmakers (the usual names – Will Hill, Ladbrokes, BetFred, SportingBet, StanJames, etc.). I’m a fairly casual bettor, but I do want the best odds for each bet, hence the large number of accounts.
So, I would say – particularly if you are going to be posting betting tips – affiliating with a large number of sportsbooks is probably a very good idea.