When is this a problem?
Using SELECT is considered hardcoding and not recommended.
It is OK to use SELECT for versions and general time periods.
Why is this a problem?
Using SELECT is hard coding and not recommended. When you use SELECT with a specific list item or time, you limit the ability to update those list items. This is especially an issue with time because a change will be required every year. You’ll need to locate every line item that references the SELECT function and make updates. These changes can only be performed by a Workspace Administrator (WSA), compared to the solution we recommend, which allows an end user to make changes.
How to correct:
Create a module with no dimensions to hold assumptions for Time, and other "SELECT" values or use LOOKUP instead of SELECT. For example, in this module, create a line item called Current Year, format it as a Time Period and select year. You can then use a lookup formula to reference this line item. When the current year changes, you update the value in that line item and it will automatically update all the formulas that reference it.
Avoiding Hard Coding
Questions on this topic? See Do any formulas use the SELECT function, especially with time? in our Model Optimization Checklist forum.