In a Fixlet with separate relevance clauses, as soon as a relevance statement evaluates to ‘false’ the Client will no longer evaluate/process the remaining relevance statements of that Fixlet. As such, it is certainly best practice to order your relevance statements in such a way as to greatly minimize the scope of applicable endpoints quickly and efficiently.
Note that this optimization also holds true within relevance statements as well with certain logical operations. For instance, if you have a statement such as:
false AND (<some complex relevance>)
false AND true
The Client will not evaluate the portion to the right of AND as the result can only be ‘false’.