Most contracts are of limited duration in large part because circumstances change and the terms of a contract could become infeasible for either party after a certain amount of time. This is no less true of a government contract.
Peculiar to public sector contracts, however, while any public employee is free to leave that job at any time for a job with better or different employment terms – in fact, every employee covered by that contract can do so – the management side is locked into the contract for its duration. In effect, then, a public contract, limited or perpetual, is really only binding upon management. Employees have the freedom to walk away at any time.
Late yesterday, the House Labor Committee passed S0713, a bill that

unilaterally mandates that existing teachers’ contracts remain in effect until a new collective bargaining agreement is reached.

The bill is scheduled for a vote in the House today, though as Will Ricci at Ocean State Republican pointed out, no advance notice has been posted of this action because the General Assembly has exempted itself from Rhode Island Open Meetings laws.
The General Assembly need to give this bill a big thumbs down. Further, it must go on to repeal the law that permits municipal contracts to continue in perpetuity. (The contract between Providence and city firefighters is a notable though certainly not the sole example.) As it is impossible to predict economic conditions and the corresponding revenue stream needed to fund these contracts, perpetual contracts are patently infeasible. The only responsible legislative course is to halt their expansion and then set about revoking all such arrangements.