Splitting the encoding in various phases...

[spoRv]

...is better than do just the final encode - at least using Avisynth, but I think it could be the same for other softwares, too.

Why?

1. Time: incredibly, splitting the works in further encodes speed a lot the whole process - for example, an avisynth script may involve source loading, color correction, grain plate; if you put the whole process in a single file, and encode it, it will take a certain time, while splitting it in three parts, may take a lot less time, from half to a quarter
   
2. Crash: everything could happen during a conversion that lasts for days... black outs, PC freeze, cat that detach the power cable - it could happen! At the contrary, if you split your encoding work in several phase, you will eventually lose just a fraction of that time
   
3. Power: a part electric power sparing - that will be not that much, but is there, you could also use a not-so powerful PC that is unable to do a complicated script, but can do small simpler things when you split the files in parts.
   

Of course, do not forget to use only lossless codecs - and the right colorspace - and delete them ONLY when you are sure you will not need them anymore... you have been warned!