25 merits would be too much. You being a good poster have received only 4 merits in last 120 days. There is no rainfall of merit that we make the requirement too much for any campaign.
Even all the spammers say this but in reality no one can do it except a few and who knows, you might be one of them
I have no problem with someone who has just joined the forum being expected to wait 3 months before joining signature campaigns - it means that they are here to contribute content rather than just to make a quick buck off signature campaigns that their associates told them about. I've seen a decent few posts recently that just copy paste articles or latch onto a keyword from the OP without addressing the actual topic, clearly made to just farm posts for a signature/bounty campaign, and there's a big problem with this being tackled on the forum in general.
My personal opinion is that there should be a minimum merit earned for all campaigns. Definitely at least 10.