Router reboot??

[#1]

Hi Everyone. 
I have a router question!  Enjoying Plus Net fibre and on a good day getting 33-35 meg speed. Over a week or so this slowly dwindles to about 25 - 28 meg.  A switch off and on of my router and I'm bang up to full speed again.  Why do I need to do the weekly reboot?  All the manuals I read seem to imply to keep the router on all the time?  Is this normal?  I'm using the NetGear router supplied. 

[#2]

Some customers do actually advocate rebooting their equipment during daylight hours. However having to do this on a weekly basis does seem a bit odd. I'd perhaps try resetting the router to factory defaults just to rule out any issues with the device's firmware.