What is peaking?
This is something most cycling fans know, but it's pretty hard to explain.
Top riders will usually have a big goal in their season. Let's imagine it's the Tour de France: their objective is to reach July in the best fitness possible, but not too tired or they won't be able to compete at an high level.
So "peaking" is based on balancing out your training and preparation races, in such a way that your fitness level is high while keeping your fatigue at acceptable levels. How can the riders do it? Well usually it envolves increasing the volume and intensity of your training up to 2 or 3 weeks before the big goal, when riders usually do the last preparation race, then keeping up the intensity but lowering the volume of the training. This allows the riders to stay in top fitness without too much tiredness.
How long can riders hold form for?
Some riders are able to hold form for months, others only have 1 month of peak form per year. I'd say that a rider can stay at absolute top form for about a month, but if the rider doesn't actually reach 100%, staying at around 90%, they might be able to hold form for 2 or 3 months while performing at an high level.
Who are the best riders (current or historical) at peaking for a race?
Armstrong was the absolute best at peaking for a race. Yeah he doped but as we all know just doping isn't enough. His main rival, Jan Ullrich, doped as much as Armstrong but was usually still getting into top form when the Tour started. Armstrong always reached the Tour in top form and he always held the form for the whole 3 weeks. Amazing planning and discipline.
Do you think it's better to race near your top form for most of the year or is it better to build towards one specific peak?
Depends on what kind of rider you are, what your goals are, etc. A TdF contender absolutely has to build towards one specific peak (which doesn't mean he can't win other races), but if you're like a Valverde or Joaquim Rodriguez I think it's a waste to do so. They're not winning the Tour even if they peak specifically for it, so might as well maintain a good level throughout the year.
Do you enjoy trying to work out who is where on their form curve and the race dynamics that creates, or would you prefer it if everyone was at the same stage so you can more concretely gauge form and ability at any given time?
Yes, I do enjoy it. If every rider was on the same form every race the strongest would always win. I like that there are some guys like Spilak who really focus on smaller races like the Tour the Romandie and Tour de Suisse, it allows them to fight it out with the big guys even if they're not beating them in the Tour.
Are you more suspicious of a rider who peaks for one event or of a rider who maintains a winning level for most of the season?
A bit of both. I'll explain more if I can later.