If the relapse involves heavy enough drinking that your body becomes alcohol dependent then you could go through withdrawal again. I was a heavy daily drinker for a number of years before I went to rehab. I suffered quite severe withdrawal symptoms whenever I stopped for even a day. I was quite alcohol dependent at this point.
I have had a few relapses since I finished rehab 3 years ago but these relapses were no longer than 4-5 days each and spread 6 months or so apart. My body hadn't become dependent on the booze so when I stopped the withdrawal was very mild. Insomnia and anxiety mostly.