/eof compiler directive to keep prototypes in source with the logic

So, I'm on a runaway train now with service programs, taking time off-hours
(I'm a contractor) to learn all of this stuff, and now stumbling onto
conditional compiler directives.

I've always disliked the idea of keeping prototypes in their own source
file, usually QPROTOSRC. So, while I was searching for information on how
to use /DEFINE, /IF DEFINED, etc., I found Jon and Susan's article at
http://ibmsystemsmag.com/ibmi/developer/rpg/iseries-extra--using-conditional-compiler-directiv/?page=2
and opened up "Code Sample 1" (pasted below), which appears to be an answer
to avoiding QPROTOSRC files. My question: Is anyone actually using this
technique? If anyone has considered using it, but decided not to, can you
explain why?

- Dan

* Source member EndOfMonth
* Ignore H-spec if only processing prototypes
/If Not Defined(OnlyProtos)
H DatFmt(*ISO) NoMain
/EndIf

D EndOfMonth Pr D DatFmt(*ISO)
D WorkDate D DatFmt(*ISO) Value

* If prototypes is all we want, then
* skip straight to end of file
/If Defined(OnlyProtos)
/EOF
/EndIf

P EndOfMonth B
D PI D DatFmt(*ISO)
D WorkDate D DatFmt(*ISO) Value

* Working variables
D DayNo S 3P 0

* Advance the input date (WorkDate) by one month

C AddDur 1:*M WorkDate

* Subtract day number from result to reach last
* day of previous month

C Extrct WorkDate:*D DayNo
C SubDur DayNo:*D WorkDate

C Return WorkDate

P EndOfMonth E