Note the two flaws here:
- If milis () skips values (which it does on many Arduino boards) then
every skip will guarantee a 1ms slip in time carries forwards into the future.
If a 1 millisecond discrepancy has ANY impact on the application, milliseconds is the wrong time frame to be using.
- If the "stuff" or "other stuff" happens to take longer than DELAY ms then
the whole sketch will slip back in time never to recover. If you were meant
to be providing time to a clock display this would be an issue.
Then, again, you are using the wrong approach.
In general, it is better to keep track of the last time something happened, and determine if now minus then indicates that it is time to do it again. I stand by not adding times.