Hey,

As you know, JEE Main is held four times a year by NTA: in February, March, April, and May. It means you have about four months to prepare for JEE Advanced following JEE Main (February). This happens, if you appear for February attempt only. If you appear for other subsequent attempts, then, the time will be deducted significantly. Generally, it is always better to do comprehensive preparation for JEE Mains and Advanced as preparing for Advanced will surely help in clearing Mains itself.