When to trade - that's an age old question. Fortunately you can't get a failing mark for answering it wrong, because there is no wrong answer, only lots of different right ones.
Everyone is different so you're going to have to weigh what works for you. RVs are a hobby, not an investment, so they don't make you money. But, you can try to lose as little of it as possible. If you get too far into the money thing though you will lose the ability to enjoy it now because you'll always be waiting for a better deal. If you can get something you really want sooner rather than later you can start enjoying it now, rather than waiting until you have one foot in the grave.
It is true that RVs are supposed to lose big time in value the first year. But that doesn't necessarily mean that has to always happen. The Internet is making more RVers savvy about what to buy and how much they have to pay. This means that RV dealers have to get in the 25% discount range to be competitive. If you find a new coach and only get a 15% discount you will lose big time the first year. If you got 25% off it can vary quite a bit, depending upon how bad the place where you want to get the second coach wants to move his new coach and how easily he can move your old coach.
When I traded my 2003 Suncruiser on a 2004 Allegro Bus all of the preconceived notions indicated that I would lose. So we planned on waiting a bit more. However, after calculating a 25% discount off the Bus, and then looking at what my "true" trade-in allowance was on the Suncruiser I found that I only lost about $10,000 on a 1 year old coach with 10,000 miles on it. My Suncruiser had a $120K MSRP and I got it for $90K and was allowed $80K after receiving a decent discount on the Allegro Bus. However, the dealer I bought from really wanted my business. Plus, he moved my trade after a couple of months and made money on it. This happened in June. 9 months earlier I priced a new 2003 Dutch Star and found that I was only being allowed a $75K trade-in on a current year coach (although it had 4,000 miles on it) so I would have lost $15K on that. But that was winter and this dealer didn't move used coaches as fast as the Tiffin dealer so they didn't want to stick that much into it.
All in all, it was an excellent choice. The 2005s are out now and the MSRP jumps up every year, plus the interest rate was nice and low when I made the move. Now we have the coach of our dreams and are enjoying every minute of it. You just can't put a price on that.
This may not be the best time of the year for a favorable trade-in allowance. It's going to depend on if this is a slow season in your area. It is up here, but then again it's zero degrees outside right now
so the only time dealers move their inventory is to plow snow from around them. I'd check around and see what kind of deals you can make. If you have a good relationship with your salesman you can probably find out when they move the most used RVs and plan accordingly. Do the math, you may lose, but then again, you might not.