Hi Mark,
As has been said it is fairly easy to add more extension sections. We officially sell the Super-Lite up to 56ft so you can effectively achieve this by just adding one section.
Unofficially we do have quite a large number of clients who have added more sections and are regularly using this pole at heights of 75ft+, whilst this is proving achievable for them we cannot recommend it due to product liability and insurance purposes. We also have not carried out testing at above the 56ft level. If damage were to occur when in use at this height it would not be covered under the poles 6 month warranty.
If you decide that you need to use it higher than 56ft then it is completely possible to do so. You would need to carry out a suitably stringent risk assessment of the task to cover your own liability issues, as is true with any high level cleaning.
As to when they are coming into stock, they are technically coming into stock next week, but all of the extension sections of this batch have been reserved already (mainly as part of 56ft pole assemblies). Another batch of 300 will be arriving by mid-July so this will ensure ready availability after that time.