Shan,

A spring support is not mandatory. Use a spring only if it is necessary. You have criteria for maximum allowed sustained stress in the pipe, maximum allowed moment on end connections and any other joints, and maximum allowed support spacing, limited by deflection, support load etc., whether that support is a solid or a spring. If you can satisfy all the criteria without a spring, don't use one.

In some circumstances you may be concerned to reduce stress due to cyclic loads by using a spring support, but this usually does not apply to a wellhead.