If we define alignement the event when all planets have the same heliocentric longitude, from Mercury to Neptune, also if we neglet the differences in latitude and the orbital inclination.
In the best case, we can consider that the planets can be in the same sector, a very narrow sector (heliocentric sector!), the minimum sector
with 8 planets is only 43° in a time span of 9000 years
http://www.pierpaoloricci.it/dati/al...netari_eng.htm