The more the better for tx propagation and block validation. I think 5000 is good enough, if it grows with the number of txs, not reduces.
5000 is not that big of a deal as number. We all know how easy it is for an entity to host hundreds of nodes from datacenters in order to gain a fair share of the total node percentage. Especially if you team with with others that do the exact same thing. It may turn out to be an expensive practice if you happen to keep them running for a long time, but depending on what the intentions are, it might turn out to be a worthwile action after all.