The average bulb life on the Mits RPTV's is about 10,000 hours with about 50% dimming and cost about $120 for OEM lamps. If your use to a projector the BenQ 1070 and Optoma HD25 are rated for about 6000Hrs but are too new to know real life expectancy. An 80" sharp LCD would solve your lamp issue but cost enough for you to replace quite a few lamps on the RPTV or projector. I would go with the new entry level DLP projectors myself if you like the projector now.
"Smart enough to know better, to old to care" ------ Dedicated Home Theater, Mitsubishi HC7900DW Projector, 110" 16:9 Jamestown screen with variable power masking for CIW 2.50:1 to 16:9, Marantz 7009 with 7.1.4 Atmos with Ohm mains,3 DIY Subs (2 15" (1 ported, 1 sealed and a 12" 4th order bandpass), 1 DIY butt kicker, Custom Built HTPC, 10TB DroboFS NAS