problem with only 3 or 4 turns on a multi is if the spool slips under your thumb when you are giving it the heave ho, you are straight onto the mainline and that is likely to snap with the sudden pressure.
There is a disadvantage in having a topshot that is too long (e.g. 2x rod length plus 50 turns on the spool).
If the line diameter changes suddenly when the cast is well under way (more than 15/20 yards of lead travel and before about 40 or 50 yards out) the knot can wrap aound rod rings or vibrate (or something like that) as it travels through them and cause either a birds nest or a snap off with a ring damaged (bent).
This happens a lot less with a tapered join between leader and main line (but manufactured leaders are usually 13m or less )
You'll probably only be using a leader this long off a pier, cliff or over ground that is extremely snaggy close in; if you have to use light main line and heavy shockleader you can go 80lb to 50lb to 25lb to 15lb but won't bother unless you have to cast hard