How risky is re-using yeast?

[BarryNL]

I brewed up some session bitter (o.g. 1.038) which I bottled last weekend and I washed and saved some of the yeast (a Wyeast 1098). I was reasonably careful, sanitising all the bottles used with Chemipro caustic soda and rinsing with tap water. I was planning to use this to brew another small batch of session beer but I fancy brewing up a strong IPA instead this weekend. I was happy that if it all went wrong I could live with dumping ten litres of session beer but 20 of IPA would be more painful.

Is reusing yeast significantly riskier than using a new pack or is it generally pretty safe - I'd make up a starter from the saved yeast if that makes a difference.

[AT]

how about say if i wanted to do a chimay clone (which i do in the future) and reuse the yeast in an empty chimay bottle, is it safe once i sanatise everything? or should i just be safe and use safale?

[spearmint-wino]

Cool tip... so are you saying flame the whole neck, or just the rim (bottle top)?