Since Florida is a warm state most of the year and has higher levels of humidity, especially in the summer, your A/C system will be running a lot of the year. Typically they last 12-15 years. A key factor in how long your system will last has to do with how well you maintain it.
The first thing having to do with maintenance of your system is replacement of filters. All filters should be replaced once a month. The dirtier they get the harder it is for air to flow through them which not only makes your system work harder but also can result in less cooling. I always had used the more expensive filters that were supposed to be better at trapping the dust particles but recently found out through an inspector that those are not good to use as they reduce air flow and make your system work harder. The inexpensive filters that are good quality are best to use as long as you replace them once a month.
The second thing having to do with maintenance is getting an A/C company to come out at least once a year to check and/or service your system. Making sure that there is adequate levels of refrigerant, drain pipes are cleared, etc. will allow your system to function better and last longer.
Keeping your system running properly by maintaining it properly will not only let you get the best level of cooling but will also save you money by lengthening the life of your system.