DOD/NRO mission integration cycle is 5 years vs the NASA 24 -36 month or the commercial 18-24 month.
Also, there is the acquisition cycle. Spacex or ULA just doesn't get the missions. There will be a solicitation, RFP and source selection.
So the set back for the first mission is longer
Yes, good point on integration lead time, at least for some missions.[1] Any extended (5yr) LV-specific integration efforts would need to start very soon, as the current EELV Phase 1 plan has all launch service acquisitions complete end FY17; fulfilled (launched) by end FY19; and with open competition for launch services starting in FY18.
While there may be "solicitation, RFP and source selection", at this time only 14 missions are potentially available for competition FY15-FY17.* The remaining missions are ULA sole source.[2] In short, ULA is guaranteed ELC through FY19 (end Phase 1 fly-out), 36 cores, and the majority of the launch service contract awards through FY17. Assuming new entrants are certified, the landscape is likely to change significantly beginning FY18. That gives
ULA everyone less than 4 years to get ready for the sequel.
[1]
USAF FY2014 Missle Procurement budget submission (April 2013)
EELV launch services are usually ordered No-Later-Than 24 months prior to the planned mission launch. EELV launch services may be ordered earlier than the standard 24 months to allow a longer integration period for first-time or complex integrations.
...
Once a New Entrant demonstrates a successful launch of an EELV-class launch system, the Air Force will award integration studies to the new entrant. Launch Services deemed as having higher risk tolerance by the Department may be awarded to service providers other than ULA as part of the certification process.
Note that certification is not required before award of integration studies. Granted, that doesn't mean a launch services contract, but it provides a head start.
[2] Ibid
The Department has designated 14 cores, for AF and other organization missions, across FY15-FY17 procurement years as open to competition based on the projected performance of the designs described by potential New Entrants in their Statements of Intent (SOI) as well as providing 36 cores to United Launch Alliance in FY13-17. If competition is not viable at time of need; missions will be awarded to the incumbent ...
* edit: To clarify, the fine print says "14 cores"[2] , not 14 missions, so the potentially competed missions might be less.