Thanks to everyone for your replies. I ran them last night for about four and a half hours with out any problem. From the calculations i made after searching the archives, I think it should run them for like five and a hlaf hours.
The calculations in the archive are strictly ballpark estimates. I strongly suggest testing in a controlled environment (i.e. simulated field testing at home) if you may often run into a situation in which you want to run the system close to its max run-time. (But maybe last night
was controlled testing?)
One thing to keep in mind: the higher the current draw and lower the battery capacity, the less efficient the setup. Reduced efficiency may change (i.e. lower) the .80 fudge factor in the run-time estimate calculations.
For example, let's take a 1000 mA draw on both a 10AH and 5AH SLA. The run-times may be calculated as 8 hrs for the 10AH, and 4 hrs for the 5AH. BUT, you're using the 5AH battery's capacity less efficiently, so you may only get 3-1/2 hrs out of the 5AH SLA (even though you calculated 4 hrs run-time).
I don't know if you'll encounter a noticable loss in efficiency relative to the calculations, but...it's worth testing out at home, IMO.