Usually, a Statute of Limitations is a time period in which a charge must be brought. Once it is filed, there is no time limit on when it is prosecuted, other than a speed trial right. Your boyfriend is not staying out of trouble, he is a fugitive and until he comes back to Florida to face his charges the situation is not going to go away.
The best thing he can do is while out of state contact a Florida attorney (there are plenty listed here) and arrange his surrender or one day he might just get picked up and spend more time waiting to be transferred to Florida than he would be sentenced to.
There is NO STATUTE OF LIMITATIONS ISSUE. First, your boyfriend was on probation which means he already pled to the charge so there is no issue of a statute of limitations because the case was successfully prosecuted with in the time frames. EVEN IF, there was a statute of limitations issue it still would NOT be applicable to your boyfriend's case because once you leave the State of Florida the statute of limitations is tolled.
As for traveling out of the country, every time someone enters the country be it at a border crossing, ship, or plane, CBP (Customs Border Protection) runs a background and warrant check on every body entering the country. If he ever leaves again he will be detained again. Next time he may not be so lucky. He has already promised once to appear and failed to do so after being detained. If Florida does decided to extradite your boyfriend will be responsible to pay for his extradition which often runs from the high hundreds to several thousand dollars.
He is better off returning to Florida and surrendering himself. If he's extradited and sent back he most likely can expect the judge to give him the 5 years Florida State Prison on the VOP charge for the cocaine.
If you have any further questions don't hesitate to contact me (800) 272-9163.