Check if you need to use step ladders inside, ensure they are clean, we always remove shoes.
Make sure you charge them more than you do for the outsides, we charge them 1.5 times normal outsode clean for doing insides, you may not be using ladders, but it's a lot more hassle. I sent a lad inside yesterday for an old granny, by the time he came out I was two houses further on before he caught up with me!!