Last seasons rooted cuttings were in 1 gallon for 1-2 months, depending on the variety. They were up potted to 5 gallon buckets when the 1 gallon pots were full of roots, but before they got root bound.
I currently have 1 gallon cuttings that were started in the fall and have not been up potted to 5 gallon buckets only because there is no space for the 5 gallon containers (it is still too cold outside).
Most small fig plants that were purchased in 1 gallon containers (Lowes, Mission below and Online) were up potted to 5 gallon buckets and grew 3-4 feet in one season (last year).

One simple visual check of the 1 gallon pots is roots are visible at the surface and also at the drain holes. I then do a lift test when the potting mix is dry, carefully lift the plant by the stem, only about 1/2 inch, if the entire root ball is lifted from the container it is ready for repotting (the visual check is always performed first).