Hello,
Your question is a bit unclear. If your question is if taking a year to solely prepare for jee mains helps, then i must say, it depends on the work you put in. If you work properly, following proper materials, then yes, there are good amount of chances for you to get a better rank. If you want to know the maximum number of times you can appear for jee mains, then the answer is 3 consecutive years.
Good Luck!