Clean the Bulb

If possible, wipe down the bulb with rubbing alcohol – and let it dry before putting in the projector.  If rubbing alcohol isn’t available, just try to wipe off any fingerprints before installing it.
The glass is thin and expands & contracts with its own intense heat it generates.  Under these conditions, simple dirt, grease and even fingerprints can potentially lessen the life of a bulb greatly.