Should I leave a builder inactive for walls?

[irmtfan]

An active farmer in th8 should farm 4m+ gold each day and/or one million gold each hour.
Any record below 4m each day is not active farmer. pay attention that i said each day. it means if you dont farm one day you should farm 8 million in the other day.
So you should farm 32M gold each week and 130m in one month.
With that rate you can upgrade to th9 after one month in th8 which is enough for max bk10 and max offense.

Upgrading walls without a free builder is 10 times harder.
You sould be able to stagger your builders how that you have a free builder every 24 hours (favorite) or 48 hours at most.

If you cannot manage your builders it is better to leave one builder free for walls. because even if you are active farmer you will block yourself with full gold storages.

Also you can upgrade to th9 with full skull + max offense so dont need to be max defense and max lab.

[Iftheskyisblue]

Organise your builder schedule so u have 1 builder finishing every day and keep them all busy. You can do that easily at TH8. only tesla upgrades are long and more difficult to schedule

[Azza03]

I am a slightly older TH8 and I also have 5 builders. When I started TH8 I kept all working, and I only got 60 skulls since I upgraded (aprox: 2 months ago). That was because I didnt keep a builder free. Just starting from today (about 2 hrs ago) I have upgraded 3 skulls while taking a few breaks!
Plus the lab takes longer then even 4 non stop builders working.

Also, if you enjoy upgrading walls, keep a spare builder. This game is for enjoyment, not a race to a maxed base.