The length of the ladder line affects the impedance at the balun and the SWR
on the coax, but this varies by band. It shouldn't be a problem with a wide-range
tuner connected directly to the ladder line.
However, if you are using a balun into coax with no tuner at that point, it will
affect the SWR on the coax, and a high SWR can increase the losses.
As an example, thefeedpoint impedance on 80m should be about 100 ohms or so.
With 50' of Wireman 551 ladder line we can use VK1OD's handy calculator: http://vk1od.net/calc/tl/tllc.php
to calculate the impedance at the balun as 630+j700 ohms at 3.5 MHz. The
SWR on the coax will be around 30 : 1 across the band. The same feedline
length on 40m (where the loop impedance is roughly 150 ohms) gives an SWR
of about 9 : 1 on the coax. With 62 feet of ladder line the SWR on the coax
is about 3 : 1.
On 20m the feedpoint will be around 200 ohms, rising to about 400 ohms on
10m. Generally multiples of 1/2 wavelength (62' on 40m) will give the lowest
SWR on harmonic frequencies, but not necessarily on 80m or on the WARC
bands. If the coax between the balun and the tuner is short then the losses
due to high SWR might be acceptable, but you may have to experiment to
find a line length that your tuner can match on all bands of interest. (It
depends on the tuner design and the length of coax.)
One approach that I had good luck with (at least for CW operation on the
pre-WARC bands) is to cut the antenna for about 3.55 MHz and feed it with
a 4 : 1 balun directly to coax at the antenna feedpoint. Typically the
feedpoint impedance at resonance varies between about 90 and 400 ohms,
giving a worst case SWR of just over 2 : 1 at the resonant points on 80, 40,
20, 15 and 10m. (This works best for CW operation because it requires a
resonance low in the 80m band to get the harmonics aligned properly.)