Well, you can install Battery Doctor as I have, and it has adjustable alerts.
But, you are not aware that the newer Lithium Ion batteries we have in the modern cellphones do NOT have a memory as you think.
That was true of the older Nickel Cadmium (Nicad) batteries.
You can top off the battery in the S5, S4, S3, etc... anytime you want to. Don't wait for it to be depleted.
I just stuck my S5 on the wireless charging pad this morning to top it off for a long weekend, and it was at 65%.
Not to worry, your battery will be fine regardless of when you decide to charge it.
But, do NOT let it get completely discharged to flat zero. That is a no no on Lithium Ion cells.