The maximum length for any systems depends on three main things that can be evaluated with Ohms Law (I=R/V):
I Igniter current rating
R Cable Resistance
V Firing Power
Cable resistance will very from manufacture so it is recommended that cables be tested if used for long runs.
firing power can depend on the type of module used and the use of external power. With the FTQ module, the internal capacitors will provide more than 20V of power.
The minimum "All-Fire" current rating of igniters will also very. A common non-regulated igniters has 600mA minimum All-Fire rating.
Users have tested and successfully fired multiple matches over 100s of feet. Some specific examples found in the fireTEK User Facebook page are as follows:
Single Chinese igniters at 450 ft with an FTH (14.8v) module with no external power
2 MJG Initiators in series on each of three rails connected in parallel with each rail running out on 100ft of cable fired with an FTH (14.8v) with no external power
The FTQ module measures and displays the firing circuit resistance and calculated firing current which can be used to asses firing capabilities of in-series connections, as shown in the video below. If you intend to fire multiple igniters in parallel and/or use multiple parallel rails split with lengthy cables it is strongly recommend to test in the same way you want to use it in the field first.