I did that for some, but most of them I didn't. Sometimes I even went on and got like 3 avatars on the same day. Just send exactly around the avie score, don't aim for trophies (some on the beggining of the month like now is fine, but no more than 2-3 as well I'd say) and do it slowly (I confess I got some of them too fast ). Nothing ever happened to my account thoiugh. Keep in mind I don't ever post on neoboards (kinda paranoid ppl see the avatar count going up way too quickly, I broke 300+ after doing this).
If you keep it slow like 1 or 2 every 2-3 days you will be fine
edit: I used (you need an account to see links) for all my timings when needed, since sometimes you can get scores too fast with the codes. That's the only other concern.
GL, it's pretty easy and safe if you use your common sense
if you (or anyose else) need anything else feel free to ask here or pm me =)