Let's assume a $100k yacht stored for 5 years at $200pm.
Loss of earning power @12% = $60k.
Depreciation 6% = $30k
Cost of going into and coming out of storage(est) = $4,000
3% = 15k (yes, it still needs to be looked after)
costs 5 * 12 * $200 = $12000
Insurance(est) = 5 * $1000 = $5,000
Total Cost = $126,000
In other words unless you are really unlucky you could sell and then buy a similar boat in near perfect condition for what you are loosing if you store your boat.