+5% per week is ok, but if you already an experience runner you can increase faster up to the base line. Base line it is avg weekly volume for your current fitness (vdot), vdot=60 is about 6h per week, vdot=70 is about 10-12h per week. Of course it depends of a lot of variables: how long you got a breake, or maybe you just started a new cycle, or post injury recovery, how hard injury was... maybe you took break one week after a marathon where you can icrease quickly mileage up to +50% every week... and so on. General rule: +5-10% per week and after 2nd or 3rd week volume step back for adaptation, also general rule is: when you start new cycle (new year, season) try to work with base volume +1h overal increase and build all training with new volume, let say last season you ran 70miles (about 6h per week avg) and you want to start a new season with 7h (about 75-78miles), you slowly build base up to 7h volume and continue work with that volume until your peak, race, etc. I was learning like this from a different respectfull coaches including cycling discipline.