I wouldn't hassle too much, they do that. Here are some of my collection testing my patience:
G pulchra 2.5cm DLS - 7 months since last molt in February
L Striatipes 8.5cm DLS - 10 months since last molt in November, previously every 30-40 days
B vagans 9cm DLS - 10 months since last molt in November, previously about 2 months
B emilia 8cm DLS - 10 months since last molt in November, previously about 50 days
There are several more but you get the picture. Bottom line is that summer heat = molting frenzy and then they close shop over winter even when they're tiny. Babies (1 - 5cm or so) will molt every 40 days or so in summer then it lengthens to 4-5 months over winter.
The only trick I know of is to buy lots of T's so that you have more chance of getting a regular molt "fix"