Is it worth doing a PGDIE course at NITIE at 29, after having a 5-year gap after graduation and a 3-year work experience in a PSU? Do placements get affected because of the age factor?

Answering such a question is a bit typical as it is important to know whether you are working or just asking. If you are working or due to some reason there is a gap of 5 years after graduation then you should have substantial reason during your PI.

Another crucial factor will be what the main reason is for the 5-year gap after graduation. Just in case,

• If you are a female candidate and left work due to marriage, childbirth, and relocation to a different city, the recruiters will tend to be more cooperative.
• If you do not have any illnesses or other severe burdens recruiters will be skeptical of hiring you as it shows that you lack the motivation to work. 
• But, if you are from PSU you would be preferred in final interviews. I would suggest you with such experience in PSU and 5 years of gap your best bet would be towards consulting. Though, it could be a bit difficult getting into FMCG.

Apart from all this, if you want to join NITIE for placements, I think the average package is pretty good now and you will get at least 15 LPA if you are a sincere person or at the worst someone will get only 10 LPA for sure. Better you prepare yourself with convincing reasons and joining NITIE would be the best option.