I did both for awhile. Breastfed all day, and 2-3 bottles at night so my husband could help. (Pumping didn't work for me).  Some babies will continue breastfeeding, others realize they don't have to work as hard to get the formula, and only take it. Its hard to tell.

If you act calm and relaxed as if you expect him to enjoy the bottle, then he will take it much better.  Cuddle him & talk to him as you do when he does breast feed.  I began Jaydee on a couple of bottles of formula a week from when he was 6mths old, then by the time he was about 10mths old, he would have at least one bottle of formula a day.  It gave us so much more freedom, & made it easier for others to babysit him when the occasion arose.

I have always expressed anyway, so he was used to the bottle & although he was a bit fussy, once we found a formula he liked it was all good.  When I first started work, he would have breast in the morning, formula during the day and breast in the evenings.  Breast is definitely a better soother & a great fall back if they wake at night - keep mixing it up for as long as it is convenient.  I never felt any discomfort, for if you slowly ease off dropping a breast feed over a period of a week or two - your body seems to know how much milk to make.

Best of luck with it.

Just thought that I would add that 60 mls is the average feed for a formula feed. I was unable to breast feed miss 6 so became quite an expert with formula. She did the exact same thing (played with the bottle) until she let me know when it was time to increase the size of the bottle. She would down it in no time flat so I knew it was time to increase the amount in the bottle to around 120 ml.

best of luck,

fiona xox

WHY DONT U TRY AND START TO STORE BREAST MILK IN THE FREEZER NOW EVEN JUS LITTLE BITS ADD UP IN CASE HE DOSENT LIKE THE FORMULA IT STORES REALLY WELL AND THE BAGS U BUY 4 EBM GIVE ALL THE INSTRUCTIONS U NEED DEFROSTING AND STORING ETC.  ANOTHER ALT. COULD B TO GIVE HIM A SIPPY CUP FOR HIS FORMULA THRU THE DAY SO THERES MORE OF A DIFFERENCE BETWEEN BM MAYBE HE'LL B MORE LIKELY TO WANT BREAST FEEDS IF HES NOT GETTING A BOTTLE, ONCE MY BABY STARTED BOTTLES SHE DIDNT WANT TO GO BACK TO WORKING HARDER FOR BREAST FEEDS. MY FRIEND DID THE SIPPY CUP AT NOT MUCH OLDER THAN URS AND IT WORKED. TOMMEE TIPPEE 'NUBI' SIPPY CUPS HAVE A SOFT LATEX TEAT SO THEY CAN SUCK IT BETTER WEN THEY LITTLER BUT ITS STILL A  SIPPY CUP SHAPE. GOOD LUCK

in my experence i have found that once you introduce the bottle and they get use to it they won't take the boob anymoe, that is just from my experience

I haven't had to do this but I would advise you find some time to express at least for comfort on those days (not necessarily to keep the milk) just enough to stop your breasts from becoming engorged.  Perhaps he might become more interested in solids if he's not all that interested in formula. If he's been exculsively breastfed up until this point he may not like the taste of fomrula. Perhaps if you mix it with BM and slowly increase the amount of formula he might get used to it quicker. 

If you're only gone a couple of days a week and the breast is always offered when you are home he shouldn't have a problem rejecting the breast. you may find he might want more feeds at night or even on days you're home to make up for it.