The main abstraction for implementing long-term orders is the order pool. The order pool represents a set of long-term orders, which sell a given token to the embedded AMM at a constant rate. The token pool also handles the logic for the distribution of sales proceeds to the owners of the long-term orders.
The distribution of proceeds is done through a modified version of algorithm from Scalable Reward Distribution on the Ethereum Blockchain. Since order expiries are decoupled from proceeds distribution in the TWAMM model, the modified algorithm needs to keep track of additional parameters to compute proceeds correctly.