Should I buy some old aggressive skates to save money or just wait and buy some brand new ones?

Mostly concerned about the plastic being brittle. Getting used would save me alot of money so i can get other things. Is there like a certain cutoff on how old they can be or signs that the structural integrity isn't good? If I do buy the used ones they probably won't be older than 20 yrs. I've bought some Rollerblade viablade triforce skates in the past and they are completely fine, but I cant really do aggressive inline in them. So, should I just save up more money to get new or just get used?