Liquid malt extract (LME) is made by boiling wort under a vacuum. This means that as the wort thickens it will not scorch. The process is beyond the equipment of most brewers.
If you have reached the stage of boiling your wort, it would be counterproductive to condense it, then reconstitute it at a future time. Much easier to spend the boil time adding hops, then chilling and pitching yeast.
Get your kit and extract brewing mastered with good sanitation, temperature control and good ingredients. Do some steeping of grains, mini mashes and then start doing ag brews. Read John Palmer's site,
link Basically walk before you run at ag.
There are steps you can take to shorten your ag brewday to maximise your hours. Some people do spread brewmaking over two days. Doc manages to do four brews in one day and renovate half the house at the same time. After you have done half a dozen all grain brews, ask again about ways to shorten your brewday and strategies for spreading the process over two days. Unboiled wort is full of bacteria and can only be kept up to 24 hours before it must be boiled to avoid soured brews.
For the moment, buy some of the 3kg paint tin brews, so that when the desire hits, you can put a brew down no matter what time of day or day of the week it is.