Reading up to 8 PWM's
What MCU are you on?

Where are you getting all those PWM signals from?

If it's from an RC receiver, then a much better solution would be to get at the multiplexed signal instead, see this page.  

If the receiver demultiplexes using a 4017, then the different servo signals will be staggered and you can re-multiplex them, simply by OR'ing the signals using diodes and a pull-down resistor.

... bottom line is that it's much easier to decode one multiplexed signal than it is to mess about with 8 inputs.