Germany is one example where a long-term infrastructure investment strategy makes a lot of sense as the infrastructure is crumbling: https://www.dw.com/en/german-infrastructure-begging-for-over.... Not all could be spent in a short time as you mention, but for economic recovery, long-term funding is probably better anyways.

To close the pension gap, Germany could also buy ETFs on borrowed money, or borrow to create a national investment fund, but that would be much too eccentric for an extremely risk-averse country.