This company has already required a Telephone Interview and a code project which I completed successfully. I have now been invited to interview, and they are very keen.
I have now found out that the interview is going to be over 2hrs 45mins being split into multiple "micro" interviews by separate interviewers on separate topics. Most of which have already been covered in part in the previous stages. Do you think this interview process is reasonable, and additionally would this raise a red flag for you based upon their value of candidates time and energy?
That is an unusually short interview cycle; I once had an interview cycle that was two full eight hour days.
You seem to think that they should be valuing your time and effort in making it out to the interview, but making good use of your time is the least important factor in the interview. The interviewers' time is far more valuable to the company than yours, of course, but that's also not relevant.
The relevant factor is: the company needs to make a decision on the basis of imperfect information about whether you will add or subtract value from the company. A bad hire doesn't just burn the salary they're paid; a bad hire drags down the productivity of the entire team, a bad hire gives other people bad information so they make bad decisions, and bad hires who become interviewers hire more bad people. A bad hire is an existential threat, particularly if the company is small.
By contrast, a good hire will not only deliver value multiple times their salary -- if you are not delivering value that is, say, 4x times what they're paying you, they should be hiring someone else -- but a good hire makes everyone else more productive too. Good hires are mentors, good hires support the mission of the team, and good hires attract more good hires.
If you had to make a hire/no hire decision today where the consequences of that decision were multiple millions of dollars of gained or lost revenue, and the success or failure of the team, would you want to make that decision with only 2 hours and 45 minutes of data? I wouldn't.
So far all my interviews have been for senior data science positions and been well under this time and formatted in a way where I feel my time is better valued and understood.
First, expect that as you gain experience and apply for more senior positions, the amount of scrutiny you receive during the process will get larger, not smaller.
Second, I'm not advocating that you let anyone walk all over you, but your focus on guarding your own time can be interpreted as a lack of understanding of the risks the company is taking on. Instead of focussing on whether the company is wasting your time in doing the due diligence to ensure a good hire, spend your time and effort on better understanding how you can prove to them that you're someone who can add value by solving their problems and working with others.