I did not do the following in my game, as I didn't understand the Disband feature at that time, but it can be a valuable thing in early Allied months. You can shore up low device pools by selectively disbanding units in order to rush replacements to other units. You have to be careful, and you can't disband a lot of the units, but you can help yourself in those early post-PH months if you make the trade-offs.
I'd be interested in hearing from others who actualy read the manual before beginning their games as to whether this tactic helps very much.
Based on his posts in his AAR (and in other threads) Andy Mac certainly believes very strongly in disbanding units to free up devices. However after taking into account the following considerations, I am not so certain that disbanding is really all that useful.
1. Early war shortage of devices is a problem primarily afflicting British, Indian and Australian LCUs. Early in the war, Australian units are not too often operating in areas where garrison requirements exist. British and Indian units on the other hand are operating in Burma and India where there are garrison requirements. Irrespective of how strong or weak a battalion is, it can't be subdivided. A weak battalion (say one with only 20 Ass Val) is just as valuable and useful as a strong battalion (one with 40 Ass Val) when it comes to garrisoning rear area bases.
2. As a generalisation, one should always create the British Empire divisions out of the at start disparate broken down sub units. This is because these divisions, with their divisional artillery parks integrated, have far greater staying and hitting power than fighting with the brigades side by side. Consequently, the Allied player does not have a surfeit of units to place in all those rear areas which need to have troops to guard against enemy paradrops or simply to maintain LOCs. Just because a base does not have a formal requirement for a garrison, it does not follow that it should be left vacant of soldiers.
3. Devices with low build rates slow down the accumulation of a massive offensive force if the objective is to attack in force on a wide front. However the build rate is not so impossibly low as to prevent the build up of a selective force. It just means that (a) only some units should have replacements turned on and (b) these offensive units may have to go onto the frontlines at only 90-95% of TOE because a particular device (say 25 pounder guns) is in short supply.