4320 Projectors

We purchased 5 Dell 4320 Projectors in July, 2013.  They were put into production October, 2013 at our College.  In the last 5 to 6 weeks we have had 3 bulbs blow out.  Is anyone else having this problem??  We have older projectors with twice the hours that are still using the original bulbs.  I feel like the projectors are overheating causing the bulbs to blow.