Maybe should really avoid Maxigain.
Depends on your goal.
IMO, MaxiGain (of course there are others, that work a bit differently) works best if you can leave 70k "untouched" for a long, long time. It will accumulate counters that translates to "Bonus Interest". After a year, you'll reach counter 12 i.e. "Bonus Interest" 1.2%. If no withdrawal causing a drop compared to previous month, "Bonus Interest" continues at 1.2%. You also get "Base Interest" i.e. 0.7* Sibor rate. "Base Interest" = 0.7 * 1.823 (Sibor rate on 2 Apr) = 1.2761.
So in summary,
If have 70k, and leave "untouched" for a year, you'll get
Total Interest = "Bonus Interest" + "Base Interest" = 1.2% + 1.2671% = 2.4761%
(Note that this 2.4761% is for 13th month onwards, and Sibor rates moves every day).
Of course, you can withdraw the interest the comes in monthly and leave just exactly 70k every month.
IMO, if 15k, other accounts like iSavvy and eSaver better.
Since you instantly get, I think around 1.85% from the start (for current eSaver promo for amounts < 50k) , compared to MaxiGain - first interest with 15k gets you 0.1% and will only reach max of 1.2% after a year.
If your goal is to top up to 70k in MaxiGain after a year, in order to get 2.4761% from 13th month onwards, then just keep the 15k there to build up the counters.