Dying for information on dyeing? Ask Bex!
You're correct. If properly prepared and stored in an airtight container, the stock solution can be used for quite a long time. I have actually used three year old stock to successfully start a new vat. Many traditional vat dyers keep a continual indigo dye vat going for 20+ years. The sludge build-up has to be dredged out every so often, but it is possible and conserves indigo dye.
Have a general knitting question? Ask here!
Yardage/ weight/ needle size/ gauge
Most magazine patterns are written to sell yarns. Luckily, many of today's best knitrags have a yarn weight guide to take care of the hardest part of substitution (ie.. Knitter's has the 1-5 number system)
If not, some will at least tell you the yardage/weight of yarn used (ie..sport @ 135 yds/ 50 gr, bulky @ 65yds/ 50 gr)
By the same token, most yarns have a recommended needle size and gauge on the label. If those numbers on the yarn you are wanting to substitute match the pattern, you're set. If not, ask me! : ) There is a nice little proportion to use if the gauges don't match, but I always suggest swatching first to check YOUR gauge with the sub yarn.
There are several other considerations, of course .... fiber content, hand, drape, coloration but once you know the weight yarn called for, the rest is more personal taste.
Discuss sock knitting here.
Toe-up rules
I prefer making my socks toe-up for several reasons. You can size & shape as you go more easily, there is no seam on the toe (I am pretty good at kitchner stitch - I just don't like doing it!), and... if you run out of yarn, you simply have a shorter cuff rather than no toe! My preferred technique for socks is two at a time (so I get the second one done before I get too bored with the pattern), toe-up on one long circular needle (magic loop style.)