I did some calculations on the amount of MPheal you need on your pet to have 1/2/3 concurrent summons at all times.
1wis - 0.12 MP/s
average summoner: Wis0.12 MP/s
maxed summoner:75wis -> 750.12 = 9 MP/s
3summons:(3Cost)/lifetime = x MP/s
2summons:(2Cost)/lifetime = x MP/s
1summon:Cost/lifetime = x MP/s
3summons 2summons 1summon
T7:Cost=120M, lifetime=13.2sec, 27M/s 18M/s 9M/s
T6:Cost=110M, lifetime=12.6sec, 26M/s 17M/s 8M/s
T5:Cost=10M, lifetime=12sec, 25M/s 17M/s 8M/s
T4:Cost=90M, lifetime=11.4sec, 24M/s 16M/s 8M/s
T3:Cost=75M, lifetime=10.8sec, 21M/s 14M/s 7M/s
T2:Cost=60M, lifetime=10.2sec, 18M/s 12M/s 6M/s
T1:Cost=45M, lifetime=9.6sec, 14M/s 9M/s 5M/s
T0:Cost=30M, lifetime=9sec, 10M/s 6M/s 3M/s
Calculations assuming a maxed Summoner(75wis):
X-9 = Y Pet Mheal (data for conversion from pet Mheal/s to Mheal level taken from the link below)
for 3 continuous summons;
T7: 83 Mheal level pet
T6: 82 Mheal level pet
T5: 81 Mheal level pet
T4: 80 Mheal level pet
T3: 76 Mheal level pet
T2: 71 Mheal level pet
T1: 60 Mheal level pet
T0: 34 Mheal level pet
for 2 continuous summons;
T7: 71 Mheal level pet
T6: 69 Mheal level pet
T5: 68 Mheal level pet
T4: 66 Mheal level pet
T3: 60 Mheal level pet
T2: 50 Mheal level pet
T1: 0 Mheal level pet
T0: 0 Mheal level pet
for 1 continuous summon;
T7: 0 Mheal level pet
T6: 0 Mheal level pet
T5: 0 Mheal level pet
T4: 0 Mheal level pet
T3: 0 Mheal level pet
T2: 0 Mheal level pet
T1: 0 Mheal level pet
T0: 0 Mheal level pet
Ps. The calculations that led to a rational number have been rounded to an
integer for the sake of simplicity using the rounding rule mentioned below.
Pet Mheal data used: https://guidescroll.com/2014/05/rotmg-pet-heal-and-mheal-data/
Data for maces Cost/lifetime: https://www.realmeye.com/wiki/maces
Rounding rule used: https://en.wikipedia.org/wiki/Rounding#Rounding_to_the_nearest_integer