Under what circumstances can the Initial Climb Area extend more than 2 nautical miles? While studying of FAA's Instrument Procedures Handbook, I noticed that on page 1-16 (Chapter 1: Departure Procedures) it defines the Initial Climb Area (ICA) as follows:


  The ICA is the segment of the departure procedure that starts at the DER and proceeds along the runway centerline extended to allow the aircraft sufficient distance to reach an altitude of 400 feet above DER elevation and to allow the establishment of positive course guidance by all navigation systems. A typical straight departure ICA extends 2-5 NM from the DER along the runway centerline extended. It is 500 feet wide each side of the runway centerline at DER, then spreads out at 15°


However, I can not understand how it is possible for the ICA to extend more than 2 nautical miles, since the maximum horizontal distance covered by an aircraft until it reaches an altitude of 400 feet above DER elevation can be found by using the default minimum climb gradient of 200 feet/NM, which corresponds to 2 nautical miles. For an ICA to extend more than 2 nautical miles, a climb gradient of less than 200 feet/NM would be required, something that violates the rules imposed by FAA.

Could someone point me in the right direction?
The definitive reference for this stuff is the TERPS, and it says that the ICA can extend to 10NM(!). See 14-1-6(b):


  Length. The ICA length is normally 2 NM, measured from the ICAB to the
  ICAE along RCL extended. It may be less than 2 NM in length for early
  turns by publishing a climb gradient. The ICA may be extended beyond 2
  NM to maximum length of 10 NM. A specified altitude (typically 400
  feet above DER) or the interception of PCG route must identify the
  ICAE.


I may have missed it, but I didn't see anything in the TERPS that explains how to set the length. However, the ICA definition from the IPH says (emphasis mine):


  Initial Climb Area (ICA). An area beginning at the departure end of
  runway (DER) to provide unrestricted climb to at least 400 feet above
  DER elevation.


I couldn't find a formal definition of "unrestricted" but in ATC-speak it usually means "go for it" (e.g. ATC Orders 4-3-2(e)(1)). In this context, though, I think it means "no lower limit" rather than "no upper limit". In other words, the ICA will be extended to allow for 'worst case' scenarios where an aircraft's climb rate is extremely limited.

That suggests hot and high airports, and if you look at the ODPs for a famously high airport like Lake County (Leadville), CO (KLXV) at 9,934' MSL you'll see that the departure procedures are indeed almost straight, e.g. 
DAVVY ONE, which is more or less straight out for 20NM from runway 34.