I usually find 3 years deployment/maintainance, 1 year overhaul to work best, particularly if you have maintainance posts set up where ships can be parked and not ticking up their clocks. The only ships that go longer are long duration scout ships, sent to explore at the fringe.
Edit: and my actual comments on the ships never posted, so slot them in here.
Invincible class Command Ship 16,000 tons 434 Crew 2844 BP TCS 320 TH 1600 EM 0
5000 km/s JR 3-50 Armour 5-56 Shields 0-0 Sensors 140/140/0/0 Damage Control Rating 13 PPV 30
Maint Life 2.42 Years MSP 1444 AFR 157% IFR 2.2% 1YR 338 5YR 5072 Max Repair 400 MSP
Intended Deployment Time: 12 months Spare Berths 2
J16000(3-50) Military Jump Drive Max Ship Size 16000 tons Distance 50k km Squadron Size 3
Large Military Magneto-plasma Drive (2) Power 800 Fuel Use 25% Signature 800 Exp 10%
Fuel Capacity 2,000,000 Litres Range 90.0 billion km (208 days at full power)
10cm Railgun V2/C3 (10x4) Range 20,000km TS: 5000 km/s Power 3-3 RM 2 ROF 5 1 1 0 0 0 0 0 0 0 0
Fire Control S01 40-5000 (2) Max Range: 80,000 km TS: 5000 km/s 88 75 62 50 38 25 12 0 0 0
Primary Fusion Reactor (1) Total Power Output 30 Armour 0 Exp 5%
Active Search Sensor MR463-R140 (1) GPS 39200 Range 463.8m km Resolution 140
Active Search Sensor MR39-R1 (1) GPS 280 Range 39.2m km Resolution 1
Thermal Sensor TH10-140 (1) Sensitivity 140 Detect Sig Strength 1000: 140m km
EM Detection Sensor EM10-140 (1) Sensitivity 140 Detect Sig Strength 1000: 140m km
This design is classed as a Military Vessel for maintenance purposes
I'd have some hesitation about making your jump ship also be your primary sensor platform. The NPR's tend to heavily target the ships with the strongest active sensors and if you lose this you not only lose your sensor coverage, you also lose the ability to retreat. I'd suggest stripping this out and putting it on a seperate ship with it's size made up to the jump limit with maintainance storage and fuel tanks, remeber you are going to want additional fuel and supplies along to resupply the fighters. This would then leave room for additional armouring of your sensor ship.
Anti-missile sensor is fine, but I'd drop the resolution on your other active down. 7000 ton is an unusual size to set your sensors for, resolution 60, 3000 ton, would probably be better and allow you to spot the more common smaller NPR ships easier.
Speed is fine for your tech level, you are already putting over a third of the tonnage into engines.
I'd consider using two smaller reactors for your weapons, as it is one lucky hit to the internals can take out your entire offensive capability.
Resolution II class Light Carrier 16,000 tons 260 Crew 2056 BP TCS 320 TH 1600 EM 0
5000 km/s Armour 4-56 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 16 PPV 0
Maint Life 3.36 Years MSP 1285 AFR 128% IFR 1.8% 1YR 172 5YR 2586 Max Repair 400 MSP
Intended Deployment Time: 12 months Flight Crew Berths 67
Hangar Deck Capacity 5000 tons
Large Military Magneto-plasma Drive (2) Power 800 Fuel Use 25% Signature 800 Exp 10%
Fuel Capacity 3,000,000 Litres Range 135.0 billion km (312 days at full power)
Strike Group
11x Kestrel II Fighter Speed: 10000 km/s Size: 8
1x Raptor II Recon Fighter Speed: 9600 km/s Size: 10
This design is classed as a Military Vessel for maintenance purposes
Pretty decent design for your tech level, speed is fine, lack of point defence isn't a problem as long as it is escorted by some PD ships. A little lightly armoured, but not too much of a problem if it is going to be standing off from the actual combat.
Kestrel II class Fighter 400 tons 3 Crew 99.2 BP TCS 8 TH 80 EM 0
10000 km/s Armour 4-4 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 0 PPV 3
Maint Life 0 Years MSP 0 AFR 80% IFR 1.1% 1YR 8 5YR 113 Max Repair 20 MSP
Intended Deployment Time: 0.1 months Spare Berths 7
Fighter Magneto-plasma Drive (2) Power 40 Fuel Use 489.16% Signature 40 Exp 25%
Fuel Capacity 15,000 Litres Range 1.4 billion km (38 hours at full power)
10cm Railgun V2/C3 (1x4) Range 20,000km TS: 10000 km/s Power 3-3 RM 2 ROF 5 1 1 0 0 0 0 0 0 0 0
Fire Control S00.5 40-2500 (FTR) (1) Max Range: 80,000 km TS: 10000 km/s 88 75 62 50 38 25 12 0 0 0
Small Fusion Reactor (1) Total Power Output 3 Armour 0 Exp 5%
This design is classed as a Fighter for production, combat and maintenance purposes
Add an engineering space - fighter to this, strip off one layer of armour to get the space.
I'd consider designing a fighter engine twice the size of your current one and using it to replace the two you have on the fighter, this would result in lower fuel consumption and an engine with a higher HTK.
Otherwise a pretty good design for a heavy fighter.