My daughter has a rescued poodle x schnauzer and I helped her today with clipping and trimming him. She has some Oster clippers with No 10 blades that were bought new. This is the third time that she has done him and the blades were struggling on the thicker slightly matted areas. His coat is impossible as it can't be kept clear of matts by grooming and needs to be kept really short to prevent it matting. We have no idea of how long blades last without needing sharpening? We would love some input from experienced people please.

How long inbetween are you leaving him & is the coat brushed regularly, as if matted it makes it ever so difficult for any blade to get through...no matter how sharp, which they should still be after only 3 times used.

He is done about every 4 or 5 weeks. He hates being groomed and the knots come back almost instantly anyway. A very badly designed designer crossbreed! Luckily he is very well behaved and tolerates the clipping well.

My mistake, she is actually using No 4 blades although she has 10 as well.

No wonder you struggled, no.4 blades work best on a clean, matt free coat. You could cut a 'channel' down the back with scissors and then try with the blade, also use a blaster to get the crud out of the coat before you start doing anything else. If you then use a no.10 it should work then you could (with regular grooming) use a longer blade.