for such a high work-load i wouldn't suggest anything by landoll that is gas/lpg powered. forkinlift is right on the money with this one. The only reason landoll designed a gas/lpg powered truck is to compete in the market for those type trucks, but they have a long way to go to get thier units competitive with the other brands effectively.
Their best trucks are the electrics but even those have thier own set of problems in high workload environments. Not to mention they require special training to operate, they do not drive or steer like any other machine and can be rather hard to get used to working in the tight spaces they are designed to work in. Oh yes, anyone that has serviced a gas/lpg powered one knows they can be a pain to service too ;o)

For thier design and application the electrics are pretty good under medium to light workloads imo.

I personally would not touch them with a barge pole, especially if they are double and treble shifting.
All LPG articulated machines suffer the same problem when worked hard, they overheat! The worst is the Flexi.
We had some at a customer who manufactures packaging and they used to get that hot we had a couple catch on fire.
The problem is they can only fit a relatively small engine because of size and there is not a lot of room around the engine for cooling, these machines also weigh aroun 6 ton so the engine is worked hard and there is a lot of hyd heat build up as they are hydrostatic.
My customer now uses electric Aislemasters with large capacity spare battery's and we have no issues.

Trucks will be working 2 or 3 shifts 6 to 7 days a week.

Depends on the application,Why do you need LP?