Market conditions can vary vastly over the life time of a gas sales contract, especially as many of these contracts are long term (even up to 25 years). It is therefore often desirable to have a means of modifying the price formula over time. The advantage of such clauses is that it allows the parties to adjust the pricing provisions over time and protects both sides against the risk of losing money in the long term. Price reviews are potentially good for a natural gas buyer if he believes that fuel prices are going to increase.

The disadvantage is that such clauses are extremely difficult to draft and that it somewhat negates the concept of a long term contract since if the parties fail to agree to the new terms of the contract, it could become invalid. It also complicates achieving FC. Price reviews are also problematic because it in fact means that the parties are not committed beyond the date of the next preview and one party may find itself out of the GSA contract (seller having invested and has no client and consumer with a power station and no gas) if no agreement can be reached.