Excellent point Debbie - the only time my luggage did not arrive this year, I had a 40 min Intl to Domestic connection at LAX, an airport I know very well. While I was able to run through 2 parkades and pass through security in record time (my inbound flight was actually 20 minutes late, leaving me 20 minutes to connect) there was no way that my luggage was going to make it.
In fact, other passengers connecting on the same flights did not make it either - I was in row 1 on the inbound, and knew exactly where to go. I didn't have any other reasonable way to book the connection, but am going to avoid that next time I travel the same route (in a few weeks)
You need to factor in change of terminals, passing through security again, and for intl travel often customs and immigration. What may work once may not work again.