Deepak is right, the license policy starts immediately and isn't tied to a GoLive date. Normally you will be audited annually, and although the time of year may vary, it will typically be in the fall, assuming your contract year follows the calendar year (you may have a different contract arrangement).
Every developer user counts, although sometimes the contract may read that developers who are SAP employees can be exempted. Your consultants count, however, if they use an SSCR key and/or access the Developer Workbench. If they are not on the project for the whole duration, but only for a short while, then be sure to not only lock the account, as Deepak suggests, but also to invalidate it in the date range. Locked accounts that are still valid are still counted in the audit. The audit does flag recently invalidated accounts, and if you are in the habit of trying to fool it by invalidating accounts ahead of the audit, then re-enabling them afterwards, that will become fairly obvious, so don't do that. However, if the invalidation is justified because they have actually left the project and are not coming back, then it is the right thing to do.
If you are worried about a brief surge of extra developers, then discuss it with your Account Rep.
Regards,
Matt
