It could be helpful to at least get a formal judgment against him for the arrears. The debt will continue to grow so long as he has no job but getting a judgment means your proof will not go cold before you can begin to pursue him to collect the medical expense reimbursements. The more time passes, the more likely things will get messy. You can pursue a judgment for unpaid debts anytime but doing it once a year in this situation wouldn’t be unusual. Pursuing judgment on each individual debt might not be worthwhile but an effort to aggregate 6-12 months of unpaid reimbursements is probably worthwhile.