i think its silly to dedicate a whole training day to such a small muscle group like bi/tri and shoulders. those muscle groups are so small and if you are pressing correctly your triceps should get hit pretty hard. if you are using correct form, most often times your triceps fail you first on bench pressing. it'll depend somewhat on the grip but more times than not your triceps are the weakest link in the chain. when i used to train triceps i usually would hit them after chest since i felt they were warmed up from the pressing. i say when i "used" to train triceps because now im doing a strength program and dont do any sissy,., er,., isolation exercises. just the main lifts, heavy too. 5X5 and very basic.
this is the first time ive used a strength routine over size and ive made some good progress. my biceps get sore from rowing and my triceps get a lil sore from pressing. but so many things come into play and everyone is different so its really hard to say. you should try both ways and see how you respond then use that knowledge to make the right program for you at the time. for instance i noticed that when i trained my bi's and tri's seperately i was always worried about them being sore on chest or back day since sore/under-recovered triceps would affect my pressing and sore or un-recovered biceps would affect my pulling exercises. so that would always worry me. i wanted to be as fresh as possible for the bigger muscle groups.
hope this helps.