We would like to be able to specify different overdue notice texts depending whether the item on loan can be renewed. If the item has reached the maximum number of renewals or is otherwise not renewable we would want to use a different notice text, usually explaining that the item needs to be returned to the library. At the moment the notice text we use has instructions on how to renew items then a section on what to do if the item cannot be renewed which is making the notice longer than we would like and all items are listed in the same list. So if we can specify separate notices depending if the item can be renewed we can send out 2 emails with clear instructions relevant to the item listed in that notice which can be much shorter.
I think you could already add a note about it being renewable or not with Template Toolkit to the list of items. We could probably help with figuring out how (see Mattermost chat or mailing list) If you want to send totally different notices (split the items between renewable and not) I am not sure if that would not make things overly complex. Especially since there is ongoing work to split by itemtype and that would add yet another dimension. See: bug 10190