Of course you shouldn't optimize unless it's the biggest bottleneck and more performance (or battery life) is desired.

C string operations might have been elegant 40 years ago, but nowadays they're like rerouting a 747 to check if office lights are on.

Strlen is doing a lot of work for little benefit. It does slow and power hungry memory accesses. Because it's scanning for terminating 0x00 byte, it needs to contain a branch -- and loop terminating branch must be a costly mis-predicted one.

C printf and friends are even more insane. It scans "bytecode" instructions from a string and does dynamic formatting. You can do format options like this:

  printf("% 0#*.*f\n", 15, 5, 1.234);

Or say print five chars of an unterminated string, left padded to total length of 10:

  printf("%10.5s\n", unterminated_str);

It won't (at least it shouldn't) crash even if 6th character is on an unreadable memory page.