Cisco :: 1720 / Maximum Log Buffer For Various Router Platforms?

I would like to define a general policy for our company to set the log buffer ("logging buffered xxx"). Currently, most of our configs use the default value of 4096, which does not store much of the history. I'd like to see more, when logged onto a router. We are using different router platforms (from old 1700 up to 39xx oder 72xx) Can you give me any hints, how large the buffer can be set on a platform? Which checks should I do to determine, how large I can set the buffer?
 
Here's an example of a Cisco 1720 router:
 
Cisco1720#sh mem
Head    Total(b)     Used(b)     Free(b)   Lowest(b)  Largest(b)
Processor   81AECE9C    17803244     5548816    12254428    12010916    11815908
I/O    2B43000     4968448     1560416     3408032     3374144     3396668
  
Cisco says: "Total = the total amount of memory available after the system image loads and builds its data structures."So, in this example, the total bytes are 17803244, which is ~ 16.9 Mbyte. So, if I allocate 64000 bytes, my total buffer will decrease to ~16,3 Mbyte.
 
I my calculation above is correct, I see no problem in defining a standard value of "logging buffered 64000" for every router platform - even under high load conditions. Since 64 kbytes is a very small value compared to the total usable memory of a Cisco 1720, newer platforms should not have any problems either.