Air helper springs are mainly used to adjust the ride height for heavy loads, as Gundog says. Motorhomes do generally have a constant heavy load, so sometimes can benefit from them, but it's not going to make for a vastly smoother ride. They can help with wallowing around and (by stiffening the suspension) reduce side to side sway somewhat. They do improve handling when properly and appropriately used, but that's not really the same as improving the ride.
You're more likely to get actual ride improvements with other things such as ensuring you have proper tire pressures for your weight or installing better shock absorbers (which depends somewhat on what criteria is "better" to you). One good shock to consider, if it's available for your chassis, are the Koni FSDs which through fancy valving act as though they are fairly compliant for gentle bumps while still being decently stiff for large ones. They are not inexpensive, but work well.
If you can get ones that are suitable, air suspension seats such as truckers use are very nice as well.
