In Settlers of Catan (like Diplomacy), is the secret to winning avoiding "peaking too soon?"
I often write that it depends on the group, but I think that's especially applicable here. If you are playing against computer AIs for instance, of course you want to maximize your VPs at every step.

In general, though, I don't think it's wise to sandbag in Catan--or to inwardly cheer bad luck. In the worst case scenario, aggressive Robber usage and trade embargos will hold you back until someone catches up with you. At that point, you can earnestly point out that you are no longer winning. Even if you're the obvious leader, as long as you have no more than 6-7 VPs, you can often arrange a mutually beneficial trade with someone desperate enough for what you have to break the opponents' embargo.

Additionally, having a powerful position gives extra resources, which can help you forge ahead or expand a lead, even if the other players are trying to stop you. If you plan to take an early lead, I think it's definitely better to go for cities and settlements, not Longest Road. Definitely avoid going for the Longest Road early in the game, until you either actually need the road, or the 2 VP are close to mattering to decide the winner. Having the card paints a target on you as a leader, and distracts attention from other possible leaders, but doesn't help you generate any more resources. Another worry is getting two cities off the gate (maybe with an early ore/grain settlement placement) but being hemmed in without a decent third building site opportunity.

I've seen players try to stay at 7 VP and hoarding resources until they can make a big break by taking Longest Road and building 1 VP worth of stuff in the same turn. It's sometimes worked, but sometimes fallen flat as savvy opponents can look at the resources you've been gathering and guess what your opportunities are. And isn't the point of pondering strategy to prepare for savvy opponents?