Generally, if stored at room temperature, past 2-3 years will give about correct results with maybe a bit lost quality. If stored in refrigerator all the time, around 5-6 years past the date will be quite ok. But, if you need maximum quality without doubt, just use fresh film, or film that is expired for only year or so AND stored refrigerated, preferably frozen all the time.
OTOH, 10 years over the date, stored mostly at room temperature, will usually produce very notable lack of quality. In slide films, this means usually loss in maximum density (black), usually with high color cast (e.g. magenta or reddish blacks). Neg films gain fog density and lower in contrast. Graininess goes up. Still, 10 years past the date may be quite usable for some purposes.