IIRC the return date/period of intended stay is sometimes interpreted (correctly or incorrectly) as the maximum period allowed by visa or upon entry (based upon what the immigration employee is likely to stamp into the passport). For USA citizens entering the EU, it's often three months and often six months for the UK, but can be a month or less for visa upon arrival countries.

The passport will need to be renewed soon anyway, so I'd do it through a passport agency if OP is near one. This would have the advantage of not being without a passport for long if international travel were suddenly required/wanted.