Collection action may be suspended temporarily:

(a) When the debtor cannot be located after diligent efforts, and there is reason to believe that future collection action may be sufficiently productive to justify periodic review and action on the claim considering the size of the claim and the amount which may be realized on it; or

(b) When the debtor owns no substantial equity in realty and is unable to make payments on the Government's claim or effect a compromise on it at the time, but the debtor's future prospects justify retention of the claim for periodic review and action:

(1) The applicable statute of limitations has been tolled or started anew; or

(2) Future collection can be effected by offset notwithstanding the statute of limitations.