I'm in the pharmaceutical science field and I think not having done any lab work in the 3rd week is not too bad. I started at about the 2nd or 3rd week but that's because my lab is fully established to do my sort of project and is quite well funded. Also, I started off with the same supervisor in my Honours degree year and my PhD is a continuation of that project. My knowledge of the field I'm in is therefore quite decent and I can do experiments without wondering why the hell I'm doing them.

Scholarships are generally 3 years but extensions are usually granted for up to 6 months without issue. Any longer than that, you'll need a strong reason. The advice my faculty is giving to students is to aim to finish in 3.5 years. Most people finish in 3.5 - 4 years, although, there are also people who take 4-5 years. Taking 5-6 years is a rarity, I must say.

Reading up on the literature is very important and you should not see it as a waste of time. It's especially important if you have had minimal exposure to your field of research prior to your PhD. However, I do understand how you feel. Being 'under-worked' can also be as stressful as being overworked. Meanwhile, you should set yourself up to start labwork as soon as your equipment and consumables are in. Be as productive as possible when you are able to start labwork. Trust me, by then, you wish you could have a break

May I ask where your lab is?