I believe that the upper limit on files *per drive* is 131,072 based on this thread

-i131072 means that there's an inode for every 131072 bytes (128 kByte) on the partition, not 131072 inodes in total...
From the mke2fs man page:

-i bytes-per-inode
Specify the bytes/inode ratio. mke2fs creates an
inode for every bytes-per-inode bytes of space on
the disk. The larger the bytes-per-inode ratio,
the fewer inodes will be created. This value gen­
erally shouldn't be smaller than the blocksize of
the filesystem, since then too many inodes will be
made. Be warned that is not possible to expand the
number of inodes on a filesystem after it is cre­
ated, so be careful decided the correct value for
this parameter.

For a partition size of say 18GB there are 18*1024*1024/128 = 147456 inodes.

Each tune will require two inodes (one for the mp3 file and one for the tag file). As the average size of files in total probably falls somewhere between 2 and 3 MB and there's an inode every 128kB I don't think the risk is very high that you'll run out of them...

Now, the hack in which there's a hierachy of symlinks built, corresponding to the existing playlists - that one could consume a lot of inodes. Still, unless you keep each tune in a [bleep]load of playlists, there still shouldn't be a problem. (Note: I might totally have misunderstood how the symlink tree works - haven't used it myself)

/Michael