Honestly the SPAU/SPDD phase for a CRM upgrade depends on how many notes and modifications you have made to your system. We can't give you a number because it varies. I have done SPAU/SPDD in one day in the dev box, but in other times you might need ten days.
If I were planning a schedule for that upgrade I would plan on spending at least four weeks in the dev system post upgrade fo the dev box(when basis hands it over to you) which includes all the code adjustment to make the dev system work again post-upgrade. However once again the more custom code and non-SAP stuff you have done... the more work during a technical upgrade.
Take care,
Stephen