An atmega8L is not an atmega2560 (256kbyte flash). You don't need a lot of time to upload a maximum of only 8kbyte.
As far as I know, the 115200 should be avoided with 8MHz. Perhaps it is too high or the actual baudrate is not accurate. I think that 38400 is a good (semi-high) value for a 8Mhz atmega8.
The 7168 seems a little low for optiboot. I have seen 7680 for optiboot.
Could you check the size of the bootloader once more ? How much does the optiboot use, and are the fuses set to the proper boot size ?
The few extra bytes can be very useful. Once you start adding things to your sketch, you need more flash memory along the way.