Can covenants be sort of "forgotten about" and have no enforceability?
Can I just do the exterior work I want to and not worry about
"someone" coming after me for doing so?
This is possible but risky. If you build a fence and no one does anything about it within the statute of limitations for doing so (sometimes codified with "adverse possession" laws), you could get lucky. But if you don't, you could be in a bad position and might have to tear down the fence and pay the attorney fees of the complaining homeowners. The statute of limitations for a covenant violation in Missouri is as follows:
516.095. Action for breach of covenant restricting land use, barred, when. — No action for breach of a covenant restricting use of land
caused or resulting from the size, height, cost or location of
buildings or other visible improvements on the premises in violation
of the covenant, including a proceeding to compel the removal of
buildings or visible improvements on the land because of the violation
of the terms of the covenant, shall be commenced after two years from
the date this section takes effect or from the date when the right of
action accrues, whichever is the later. Notwithstanding the
provisions of any section of the statutes tolling the statutes of
limitations, saving any causes of action which may have been otherwise
barred thereunder, establishing a time when a cause of action accrues,
or excluding certain lands from the operation and effect of any
statute of limitations, no disability or lack of knowledge on the part
of anyone shall suspend the running of the two-year period; and for
the purposes of this section, the right of action shall be deemed to
accrue immediately upon the completion of the building or visible
improvements which are in violation of the covenant.
Real estate covenants "run with the land" and are not subject to automatic expiration after a period of time, although there is a deadline to enforce acts taken in violation of the covenants. And, often, any property owner in the subdivision can enforce a covenant violation, even though only the HOA in operational good standing can continue to operate it and approve changes.
It may be necessary to resurrect the HOA and architectural control committee to obtain approval. It might also be possible to get the neighbors to agree to abrogate and terminate the covenants.