New Bass Strait ferries due mid-2020s

The Bass Strait ferry twins have just had a makeover and are attracting record numbers of passengers, but the Tasmanian government admits the vessels won't last forever and is putting money aside for an upgrade within a decade.

Profits from Spirit of Tasmania operator TT-Line will be channelled into a vessel replacement fund which is set to contain $80 million by June 2018, with the government eyeing an early-to-mid 2020s upgrade.

"The success of our policy to invest in the refurbishment of the vessels, increase day sailings and reduce fare prices has allowed the Spirits to generate money that will be used to fund their own replacements," Treasurer Peter Gutwein said.