I'm a mother who has worked away for periods of time. feel free to judge.
When dd was a baby I worked away 4 days a week for 12 weeks at a time. I was a single parent.
DD is fine, she is a happy healthy well grounded 10/11 yr old. She doesn't remember at all.
In the last 5 years I have had to be away from home approx 2 nights a week on average, DP also works full time but would deal with any child related needs such as illness etc whilst I was away.
It made great financial sense, my job was very well renumerated, our lifestyle is very good because of the role I had. I also got to spend more quality time with DP and the children than I would if I had been doing the same job more locally.
I only worked 4 days a week so Fridays I did school pick ups/drop offs. Any shopping etc was done whilst kids at school. If the kids were off we had fun days and weekends we were all able to enjoy each other because all shopping etc was already done either online/when kids were at school.
It was tough, especially when the kids got old enough to miss me and know that I would be away.
It was tough on my dp as well, he did felt that I was away having a whale of a time while he was at home doing the drudgery.
The reality was that I was working 24/7 whilst away and missing him and the kids.
I now work locally but was very lucky to land a job with a large corporate on my doorstep. I work 5 days a week again but I am home every night.
I do find I have less quality time with the kids now as does dp but I don't want to be away during the week anymore.
I would say that if I hadn't taken the roles I did we would not be in the position we are now with lifestyle etc. I wouldn't have got the job I have now without those experiences.
In my opinion, you would be unreasonable to say no, it sounds like your partner would like to do it, also although it may not seem as though there is any benefit now, there certainly will be long term.
It is only 6 months, that will fly by and you will have three days every week where you can spend time together.
Things like shopping can be done online, he can do bits and pieces on Fridays. its not easy having a partner working away but it can also help enhance family life in many ways.