Yes, certainly, if they don't believe you. They may well ask where your friends live and how long you plan to stay with each of them, what tourist sights you plan to visit, whether you have looked into hotels, b&b's, hostels, where the evidence is that your friends are happy for you to stay with them. They can ask whatever they want, and one of the most common reasons for visit visas to be refused to people who want to stay for a long time is 'the applicant showed little knowledge of the UK or of what he planned to do while here. I therefore do not believe that he is seeking leave to enter for the purposes of tourism'.
You can't 'play it by ear' for six months. And it's not really a good idea anyway. If you are going to spend that much money and time, do your research first!
Vicky