I'm traveling to Las Vegas for a conference, and unfortunately my flight arrive several (4-5) hours before check-in, and my flight out is several (4-5) hours after check out. It'd be nice to be able to wander the Strip since this is my first time here, but I don't want to be hauling my luggage around while I kill time. I'll be staying at a hotel on the Strip. Are there luggage lockers or anything similar that would be possible to use?
Hotel Luggage Storage
Your hotel will most probably allow you to store luggage before check-in and after check-out. This tripadvisor thread indeed seems to agree with this hypothesis. To confirm this you can try contacting your hotel.
Airport Luggage Storage
There used to be luggage storage facilities in Las Vegas McCarran Airport. As of may 2016 these seem to be discontinued.
There is also a private paying service called BagsToGo which offers luggage storage facilities. Quoting from their website:
3. What are the service offerings?
Baggage Storage: Allows passengers to store bags at the Fort Lauderdale-Hollywood International Airport and in Las Vegas at our Off-Airport location for up to 30 days, with valid I.D. and proof of travel within the requested storage time.
5. How much does it cost?
For Baggage Storage, the cost is $7 per bag, per calendar day.