Access is what determines whether periodic work happens
It is easy to agree a periodic programme on paper and considerably harder to deliver it in a building where every machine has to travel through a shared lift. Booking is competitive, other contractors want the same windows, and a building manager balancing several requests will not prioritise a cleaning schedule agreed months earlier between two other parties. Nobody in the building has any reason to prioritise a schedule agreed elsewhere.
That means the access arrangement should be settled at the same time as the programme rather than afterwards. A dated programme with no lift arrangement behind it will slip, and each slippage looks like a contractor failure when it is actually a scheduling one. Establishing the window first produces dates that hold, which is what a committee is actually buying. Dates that hold are what a committee is actually paying for.
