In the "old days" you would be safe in that thought, not as much in today's economy.
The state government is much more aggressive in going after any and all forms of revenue. The state will catch many more "evaders" these days and even provide a bonus system for "revenuers" to catch Fl. tax dodgers.
The state is aware of the excuses and have heard them all, remember it is up to you to prove compliance not the other way around (think tax audit)
You can and will be audited and if you have remained in the state for 30 days after buying a boat in the state will be required to pay state sales tax (popping over to Bimini for a weekend no longer counts). They will check your marina lease, insurance and see if you paid for hurricane coverage etc.) My attorney was very clear on this.
Use tax and surtax will become due when you title and/or register the boat in Florida. Florida titling and/or registration must occur:
• Within 30 days after purchase.
• Within 90 days after the boat enters Florida, if the boat is documented, titled, and/or registered in another state.
If the boat is 5 net tons of measurement or larger, the purchaser may obtain a set of
Florida Department of Revenue boat decals, which authorize the boat to remain in Florida
waters up to 90 days after the purchase. This period may be extended to 180 days with the
purchase of a 90-day extension decal. The decals must be obtained from the selling dealer
or broker.
http://dor.myflorida.com/dor/forms/2011/gt800005.pdf