If the plan is to be on the road next season the time to buy is now. You might even be a bit late. IMO the best time to buy is right after the season when people are tired of their current unit, don't want to pay/do the winter mothballing, & don't want to pay for winter storage. They just want to be rid of it.
If you have done your research & have narrowed your possible models down, you wait & watch the ads online like a hawk. If the model you are after is common, good for you, make an offer or wait till the next comes along. If the model is abit of a rare one be prepared to jump on it, travelling further to get it if necessary.
Spring is too late. Everyone is out looking then & the price is up.