When specializing on arms I hot them 2x per week, 1 time on their own day, hard and heavy, then I hit them after chest and back and go for light and fast, this has worked well for me. Here's my split which leaves lots of time to heal
day 1 chest/calves and light fast triceps
day 2 back/shoulders and light fast biceps
day 3&4 rest
day 5 bis/tris
day 6 quads/hams/calves/abs
day 7 rest