A Last Will and Testament can be challenged in Florida but the timeframe to do so is not always open-ended.
Florida law provides a mechanism for any interested person (beneficiary, creditors, etc.) to be put on a "time-clock" to object to a Will. The document that starts the clock is known as a Notice of Administration. Section 733.212(3) Fla. Stat. provides that "[a]ny interested person on whom a copy of the Notice of Administration is served must object to the validity of the Will....by filing a petition or other pleading requesting relief in accordance with the Florida Probate Rules on or before the date that is 3 months after the date of service of a copy of the notice of administration on the objecting person, or those objections are forever barred."
Take, for example, a situation where Grandma dies and someone finds a Will dated in 2005. However, Grandma actually has a Will executed in 2008 as well. If someone then files a petition seeking to have the 2005 Will admitted to probate and serves an heir with a Notice of Administration relating to the 2005 Will, the heir must file a petition challenging the 2005 Will. The basis would be that the 2005 Will is not Grandma's most current Will, i.e. the 2008 Will is the one which should be probated. If the heir does not timely challenge the 2005 Will after being served with the Notice of Administration, then the heir loses the right to challenge the 2005 Will. However, if no Notice of Administration is served, then the heir can challenge the Will even after it has been admitted to probate.
If served with a Notice of Administration, a person should seek legal assistance from an experienced probate attorney.